timeline: commit to the action log on drag and drop.

https://bugzilla.gnome.org/show_bug.cgi?id=741668
titleeditor: Make sure to set default values and update widget afterward

And make default background black, because of: https://bugzilla.gnome.org/show_bug.cgi?id=681447

https://bugzilla.gnome.org/show_bug.cgi?id=741670
Port the timeline to Gtk+ and remove clutter dependency!