timelinepipeline: make the caps from encoding profile writable

https://bugzilla.gnome.org/show_bug.cgi?id=703121
timelinepipeline: fix caps leak
ges-launch: make it portable to all locales.

Call setlocale (LC_ALL, "") as per setlocale man page
to make ges-launch portable to all locales (instead of default
"C" one).

Fixes g_option_context_parse on:
$ ges-launch-1.0 --verbose -r -q /home/prahal/Vidéos/Test3.xges -o
file:///home/prahal/Test3.mpeg
Error initializing: Invalid byte sequence in conversion input

The accentuated character in "Vidéos" the french xdg user directory
for "Videos" is what is choked upon.

https://bugzilla.gnome.org/show_bug.cgi?id=702425
formatters: Save and load bindings applied to sources.
track-element: Remove duration_changed virtual method.

We use notifies for the properties.
	+ Use notifies in audio-transition and video-transition
internal: Fix typo in the header

ges_base_xml_formatter_add_control_bindingi was meant to be
ges_base_xml_formatter_add_control_binding
container: Make initiated_move a read only protected member

It is a interesting information for subclasses.
Conflicts:
	ges/ges-container.c
ges: Move GESTimelineElemt vmethod implementation from container to clip

This is where they belong to has they are specific to that
implementation of the baseclass
container: Fix the way we check priority of subclasses when grouping objects

The resulting list was from lower to higher, we need the contrary
track: Update gaps only when commiting

We were still updating them at useless moments, do it only when absolutely needed.
internal: Add a macro to make it easier to get the end of a TimelineElement
clip: Never try to set the start after the end of an element when trimming
docs: Misc documentation fixes
container: Update offsets in GESTimelineElement vmethod implementations

So subclasses just have to link up to resync offsets
ges: Move ges_clip_edit to GESContainer

This exact same method will be needed in GESGroup, so we should have the method
in the common parent class.

API:
    - ges_clip_edit
    + ges_container_edit
    + GESContainer->edit vmethod
container: ges_container_ungroup return a transfer full list
base-xml-formatter: s/ducation/duration/
container: Let subclasses decide when height change should be computed

API:
   - GESContainer.compute_height vmethod
   + _ges_container_set_height
ges: Avoid leaking the timeline when grouping containers
container: "Implement" the set_priority vmethod

This way we will just accept any value setted