Merge branch 'refactoring_timeline' of git://anongit.kde.org/kdenlive into feature/adding-new-overlays
I added three "safe zone" overlays. All of them are the first three Farid's (afarid) suggestions:
Center - Adds lines dividing the frame in half vertically and horizontally. Center Diagonal - Adds lines connecting opposite corners. Thirds - Adds lines dividing the frame in thirds vertically and horizontally.