Don't use "type" of source, use "id" of source

The naming here is a poor choice, a source type determines if a source
is either a regular input, a filter, or a transition.  The ID is the
actual unique identifier of a source.
Remove duplicate 'strref_isempty'
(API Change) Rename obs_sceneitem_info structure

Change obs_sceneitem_info structure to obs_transform_info - this
structure will not just be used with scene items in the future.
(API Change) Rename obs_source_get(/release)frame

Renamed functions:
- obs_source_getframe (rename to obs_source_get_frame)
- obs_source_releaseframe (rename to obs_source_release_frame)

For the sake of consistency and helping to get rid of the "squishy
function name" issue
(API Change) Rename 'source_frame' + related

For the sake of naming consistency with the rest of obs.h, prefix this
structure and associated functions with obs_.

Renamed structures:
- struct source_frame (now obs_source_frame)

Renamed functions:
- source_frame_init (now obs_source_frame_init)
- source_frame_free (now obs_source_frame_free)
- source_frame_create (now obs_source_frame_create)
- source_frame_destroy (now obs_source_frame_destroy)

Affected functions:
- obs_source_output_video
- obs_source_get_frame
- obs_source_release_frame
(API Change) Rename order_movement

Prefix with obs_ for the sake of consistency

Renamed enums:
- order_movement (now obs_order_movement)

Affected functions:
- obs_source_filter_setorder
- obs_sceneitem_setorder
(API Change) Rename allow_direct_render enum

For the sake of consistency, changed allow_direct_render to
obs_allow_direct_render
(API Change) Rename filtered_audio structure

Reanmed filtered_audio to obs_audio_data, to improve the naming and
prefix with obs_ for the sake with consistency with the rest of the API
(API Change) Rename source_audio structure

Rename source_audio to obs_source_audio to make it more consistent with
the rest of the API
(API Change) Split obs_source_gettype

Changed:
- obs_source_gettype
To:
- enum obs_source_type obs_source_get_type(obs_source_t source);
- const char *obs_source_get_id(obs_source_t source);

This function was inconsistent for a number of reasons.  First, it
returns both the ID and the type of source (input/transition/filter),
which is inconsistent with the name of "get type".  Secondly, the
'squishy' naming convention which has just turned out to be bad
practice and causes inconsistencies.  So it's now replaced with two
functions that just return the type and the ID.
(API Change) Un-squish obs_sceneitem_*

Renamed:                         To:
-----------------------------------------------------------
obs_sceneitem_getscene           obs_sceneitem_get_scene
obs_sceneitem_getsource          obs_sceneitem_get_source
obs_sceneitem_setpos             obs_sceneitem_set_pos
obs_sceneitem_setrot             obs_sceneitem_set_rot
obs_sceneitem_setscale           obs_sceneitem_set_scale
obs_sceneitem_setalignment       obs_sceneitem_set_alignment
obs_sceneitem_setorder           obs_sceneitem_set_order
obs_sceneitem_getpos             obs_sceneitem_get_pos
obs_sceneitem_getrot             obs_sceneitem_get_rot
obs_sceneitem_getscale           obs_sceneitem_get_scale
obs_sceneitem_getalignment       obs_sceneitem_get_alignment
(API Change) Remove obs_graphics()

API Removed:
- graphics_t obs_graphics();
Replaced With:
- void obs_enter_graphics();
- void obs_leave_graphics();

Description:
  obs_graphics() was somewhat of a pointless function.  The only time
that it was ever necessary was to pass it as a parameter to
gs_entercontext() followed by a subsequent gs_leavecontext() call after
that.  So, I felt that it made a bit more sense just to implement
obs_enter_graphics() and obs_leave_graphics() functions to do the exact
same thing without having to repeat that code.  There's really no need
to ever "hold" the graphics pointer, though I suppose that could change
in the future so having a similar function come back isn't out of the
question.

Still, this at least reduces the amount of unnecessary repeated code for
the time being.
(API Change) Unsquish libobs (base) names

Previous names:             New names:
-----------------------------------------------------------
obs_view_setsource          obs_view_set_source
obs_view_getsource          obs_view_get_source
obs_source_getdisplayname   obs_source_get_display_name
obs_source_getwidth         obs_source_get_width
obs_source_getheight        obs_source_get_height
obs_filter_getparent        obs_filter_get_parent
obs_filter_gettarget        obs_filter_get_target
obs_source_filter_setorder  obs_source_filter_set_order
obs_source_getsettings      obs_source_get_settings
obs_source_getname          obs_source_get_name
obs_source_setname          obs_source_set_name
obs_source_setvolume        obs_source_set_volume
obs_source_getvolume        obs_source_get_volume
obs_scene_getsource         obs_scene_get_source
obs_scene_fromsource        obs_scene_from_source
obs_scene_findsource        obs_scene_find_source
obs_output_getdisplayname   obs_output_get_display_name
obs_output_getname          obs_output_get_name
obs_encoder_getname         obs_encoder_get_name
obs_service_getdisplayname  obs_service_get_display_name
obs_service_getname         obs_service_get_name
(API Change) Use 'get' convention in libobs (base)

Instead of having functions like obs_signal_handler() that can fail to
properly specify their actual intent in the name (does it signal a
handler, or does it return a signal handler?), always prefix functions
that are meant to get information with 'get' to make its functionality
more explicit.

Previous names:             New names:
-----------------------------------------------------------
obs_audio                   obs_get_audio
obs_video                   obs_get_video
obs_signalhandler           obs_get_signal_handler
obs_prochandler             obs_get_proc_handler
obs_source_signalhandler    obs_source_get_signal_handler
obs_source_prochandler      obs_source_get_proc_handler
obs_output_signalhandler    obs_output_get_signal_handler
obs_output_prochandler      obs_output_get_proc_handler
obs_service_signalhandler   obs_service_get_signal_handler
obs_service_prochandler     obs_service_get_proc_handler
(API Change) Unsquish libobs API callback names

Renamed:                    To:
-------------------------------------------------------
obs_source_info::getname    obs_source_info::get_name
obs_source_info::getwidth   obs_source_info::get_width
obs_source_info::getheight  obs_source_info::get_height
obs_output_info::getname    obs_output_info::get_name
obs_encoder_info::getname   obs_encoder_info::get_name
obs_service_info::getname   obs_service_info::get_name
(API Change) Use 'get' convention: API callbacks

Renamed:                       To:
-------------------------------------------------------
obs_source_info::defaults       obs_source_info::get_defaults
obs_source_info::properties     obs_source_info::get_properties
obs_output_info::defaults       obs_output_info::get_defaults
obs_output_info::properties     obs_output_info::get_properties
obs_output_info::total_bytes    obs_output_info::get_total_bytes
obs_output_info::dropped_frames obs_output_info::get_dropped_frames
obs_encoder_info::defaults      obs_encoder_info::get_defaults
obs_encoder_info::properties    obs_encoder_info::get_properties
obs_encoder_info::extra_data    obs_encoder_info::get_extra_data
obs_encoder_info::sei_data      obs_encoder_info::get_sei_data
obs_encoder_info::audio_info    obs_encoder_info::get_audio_info
obs_encoder_info::video_info    obs_encoder_info::get_video_fino
obs_service_info::defaults      obs_service_info::get_defaults
obs_service_info::properties    obs_service_info::get_properties
(API Change) Unsquish obs_data_* names

Changed:                 To:
-----------------------------------------------
obs_data_getjson         obs_data_get_json
obs_data_getstring       obs_data_get_string
obs_data_getint          obs_data_get_int
obs_data_getdouble       obs_data_get_double
obs_data_getbool         obs_data_get_bool
obs_data_getobj          obs_data_get_obj
obs_data_getarray        obs_data_get_array
obs_data_setstring       obs_data_set_string
obs_data_setint          obs_data_set_int
obs_data_setdouble       obs_data_set_double
obs_data_setbool         obs_data_set_bool
obs_data_setobj          obs_data_set_obj
obs_data_setarray        obs_data_set_array
obs_data_item_getstring  obs_data_item_get_string
obs_data_item_getint     obs_data_item_get_int
obs_data_item_getdouble  obs_data_item_get_double
obs_data_item_getbool    obs_data_item_get_bool
obs_data_item_getobj     obs_data_item_get_obj
obs_data_item_getarray   obs_data_item_get_array
obs_data_item_setstring  obs_data_item_set_string
obs_data_item_setint     obs_data_item_set_int
obs_data_item_setdouble  obs_data_item_set_double
obs_data_item_setbool    obs_data_item_set_bool
obs_data_item_setobj     obs_data_item_set_obj
obs_data_item_setarray   obs_data_item_set_array
(API Change) Unsquish libobs/util

Changed:                      To:
-----------------------------------------------------------
dstr_isempty                  dstr_is_empty
cf_lexer_gettokens            cf_lexer_get_tokens
cf_preprocessor_gettokens     cf_preprocessor_get_tokens
(API Change) media-io:  Improve naming consistency

Renamed:                        To:
-----------------------------------------------------------
audio_output_blocksize          audio_output_get_block_size
audio_output_planes             audio_output_get_planes
audio_output_channels           audio_output_get_channels
audio_output_samplerate         audio_output_get_sample_rate
audio_output_getinfo            audio_output_get_info
audio_output_createline         audio_output_create_line
video_output_getinfo            video_output_get_info
video_gettime                   video_output_get_time
video_getframetime              video_output_get_frame_time
video_output_width              video_output_get_width
video_output_height             video_output_get_height
video_output_framerate          video_output_get_frame_rate
video_output_num_skipped_frames video_output_get_skipped_frames
video_output_total_frames       video_output_get_total_frames
(API Change) libobs/callback: Unsquish names

Renamed:                  To:
-------------------------------------------------
calldata_getdata          calldata_get_data
calldata_getint           calldata_get_int
calldata_getfloat         calldata_get_float
calldata_getbool          calldata_get_bool
calldata_getptr           calldata_get_ptr
calldata_getstring        calldata_get_string
calldata_setdata          calldata_set_data
calldata_setint           calldata_set_int
calldata_setfloat         calldata_set_float
calldata_setbool          calldata_set_bool
calldata_setptr           calldata_set_ptr
calldata_setstring        calldata_set_string