Multiselection : remove all selected subtitltes

Issue : none

Allow removed all selected subtitles, instead of only the current

Signed-off-by: juiice <decaen.julien@gmail.com>
Add undo/redo

Issue : none

Add actions history managment with undo/redo
- Ctrl + Z : undo
- Ctrl + Maj + Z : redo

Signed-off-by: juiice <decaen.julien@gmail.com>