Use GObject.Object instead of Signallable
mainwindow: Avoid using app to access the current project
pipeline: Remove unuseful 'format' parameters and fields
pipeline: Remove duplicate check of position value
dogtail: Update dogtail tests to run on latest Gtk
dogtail: Fix tests depending on click items in the main menu
dogtail: Integrate big helper method in test method
dogtail: Cleanup test_effects
mainwindow: Cleanup the method for creating the stock icons
mainwindow: Show a title when the startup wizard is visible
timeline: Get rid of some clip animations

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=719348
mainwindow: Remove a vbox element which is not useful
mainwindow: Consistent imports and move dead code around
clipproperties: Fix effect configuration UI destruction

The second resetKeyframeToggleButtons call was raising an exception.
previewers: Fix initial value of AudioPreviewer.lastUpdate
video previewer: remove unused self._callback_id
previewers: Always set lastUpdate when computing geometry
previewers: Avoid removing sources already running

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=726904
mainwindow: Better default placement for panes

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=702507
dogtail: Fix test_backup