Second alpha release for the new version of Pitivi based on GES.
All the improvements from 0.91, plus:
* Fix a bug where transitions would stop working
* Fix the handling of rendering parameters
* Fixes for the keyframes UI in the timeline
* Usability improvements for the welcome dialog
* Update the preview immediately when adding an effect
* Fixes for AppData XML spec compliance
* Various build and packaging fixes
* Drop the PyXDG dependency
* Translations have been updated
