[pitivi] (9 commits) ...Merging translations

[Edward Hervey <edwardrv src gnome org>]

Summary of changes:

  5578b04... Revert "ui.timeline: seek playhead to mouse position on but
  10c80fd... tests: move Selection unit test to Link unit test.
  ec77f4b... previewer: add config option / preference to disable previe
  8927470... Revert "timeline.timeline: selection tracks individual trac
  1d28b45... Fix Timeline.groupSelection and Timeline.ungroupSelection.
  5af94d0... Re-enable group and ungroup actions
  cec9484... Make group and ungroup sensitive (or not) based on the curr
  6325326... Fix group/ungroup sensitiveness a bit more.
  8c14207... Merging translations