clipproperties: Use a symbolic icon for the "Remove effect" inline tool button
Fixed wrong tags
Port to the new GES API
clipproperties: Move the "Remove effect" button below the list and refactor code
Finish the port to the new GES API
Cleanup and compact some code
clipproperties: Refactor the way we create the initial infobar
clipproperties: Hide the effects toolbar when nothing is selected
clipproperties: Bring back the checkbox to enable/disable effects
dogtail tests: Fix the preferences and effects tests