tests: integration: Add a list tests only option

Also add an empty filed in the GOptionEntry array avoiding segfaults
tests: integration: PNG file was renamed to png.png
tests: integration: Rework the way we handle seeking while fully paused

The idea is that we should first play until the time we reach the first
position, at that point we PAUSE the pipeline, then, afterward do the
seeks as asked.

If we get the position before the ASYNC DONE, just accept it.
ges-formatter: Check if directory of URI is writeable

https://bugzilla.gnome.org/show_bug.cgi?id=679941
formatter: Remove the unsed can_save_uri vmethod

This virtual method does not make much sense right now, we might need it
again later, but most probably with a sensibly different API so removing
it for now.
pipeline: Remove the dynamic lock

We actually do not need it has everywhere where we would need it we are
already locked against the timeline.dyn_lock, we need to make sure it is
always the case in the future.

The hierarchy of the mutex was wrong and could possibly lead to
deadlocks
formatter: Plug leaks in the can_save_to_uri method

https://bugzilla.gnome.org/show_bug.cgi?id=679941
integration: make test_basic be two concatenated clips.
basexmlformatter: Only set timeline auto transitions when done loading.
pipeline: add a get_mode method.
ges-audio-track: Change contructor prototype.

We return an AudioTrack.
timeline: when there are no objects anymore, set duration to 0.
container: resort children after prepending an element.
trackelement: update control bindings correctly.

When duration or inpoint change, we need to remove edge control points,
and set new control points with interpolated values.
Also when duration == 0, we need to remove all control points, as otherwise
the controller will raise !is_end assertions.
It's the duty of the application to set keyframes back when duration gets
!= 0 again.
trackelement: split bindings correctly.
tests: Fix make distcheck

We need to make sure that we can write to the directory where we save
project files, so doing it in the tmp folder.

+ Properly dist test data files
tests: Give more debugging info when samples could not be generated
tests: fix NULL pointer dereference, ternary operator silliness and message type use
python: Do not initialize GES at import time
integration: Add titles test