Unify obs_data_get* and obs_data_item_get* functions handling
Unify obs_data_set* and obs_data_set_default_* function implementations
Refactor set_item(_def) to only look up items if no item is supplied
Refactor obs-data internals to forward reallocation results to callers
Unify obs_data_set* and obs_data_item_set* funtion implementations
Move obs-data accessor value handling logic into static helper functions
Change semantics of obs-data default values

Default values are now permanently stored in the obs_data_items and
can be accessed via the new get_default functions

Also default values are no longer serialized to JSON to ease transition
to new default values
Add obs-data autoselect functions

These are meant to reflect auto-detection configuration changes that
should not be written to the config, for example, frame rate changes
for a camera where the (user-/config-file-)configured frame rate isn't
available but a similar frame rate can be automatically chosen
Make properties-view reflect autoselect settings (for property lists)
Merge pull request #116 from palana/obs-data-changes

obs-data default value semantics change and autoselect value introduction