check: Bump the GNonLin and GES dependencies to 1.4.0
ui: Make media/effects library search entries placeholder text translatable
viewer: Do not forget to set ViewerWidget sink when setting our pipeline

Making the expose call working when we need to redraw the viewer.

+ Rename Pipeline._glimage_sink to Pipeline.videosink and making it
  public and simpler to read.

Conflicts:
	pitivi/mediafilespreviewer.py
check: Do no require GNonLin if GES version >= 1.5.0

As it will be directly integrated in GES itself
check: Fix variable naming
viewer: Do not call the expose function when we set the aspect ratio

During caps renegotiation resulting from the change of the video
height/width, aspect ratio changes, there is a race in glimagesink where
we end up with the viewer displaying broken frames calling the expose()
method of the sink at the same time.

Avoid calling the videosink.expose() while we change the resolution
in the pipeline.

https://bugzilla.gnome.org/show_bug.cgi?id=739145
Updated Polish translation
Correct some verb tenses in the French translation

"Met en pause" looked particularly odd in the rendering progress dialog
Added Serbian translation
Updated Czech translation
Updated Czech translation
Updated Czech translation
viewer: fix alignment
undo: Undo redo logic for assets is now implemented in project.

https://bugzilla.gnome.org/show_bug.cgi?id=739251
undo: Disconnect from the signals correctly.

https://bugzilla.gnome.org/show_bug.cgi?id=739251
mainwindow: improve signal disconnecting.

https://bugzilla.gnome.org/show_bug.cgi?id=739251
Start implementing scenario serialization

https://bugzilla.gnome.org/show_bug.cgi?id=739251
scenarios: add the type of the added asset

https://bugzilla.gnome.org/show_bug.cgi?id=739251
scenario: serialize action even if running

https://bugzilla.gnome.org/show_bug.cgi?id=739251
scenarios: serialize asset removed

https://bugzilla.gnome.org/show_bug.cgi?id=739251