TODO :
[x] Unify all the places where cursor mode is applied
[x] Fix backward playing with floating cursor
[x] When floating cursor reach the end, move the view back to start
[x] When hitting play with floating make sure the cursor is in the view. If not, make it on the left/right(backward)
[x] Expose floating cursor position in the settings
[x] Disable frame changing while in centered mode
[ ] Restore previous timeline position when hitting "ESCAPE"
[ ] Optimize refresh : when using floating cursor, do not refresh when the cursor is not on the edge