Sequencer improvements

[TimGroeneboom]

See video for demonstration. Build & run sequencer demo to observe changes

• added undo / redo / rollback system
• added coloring of segments
• adding the ability to lock segments, preventing them from moving on the track
• adding the ability to hit CTRL and move complete track from the drag position or just dragging one segment

sequencer_upgrade.mp4

[cklosters]

Thanks for the PR, I'll have time to properly review it beginning of next month.

[cklosters]

Great change, my only concern relates to deserializatrion of pointers & threading - see review comments

[cklosters]

When I drag an event (make an edit) and try to re-load the change I get the following assert (Debug / MSVC):

history_edit_error.mp4

[TimGroeneboom]

When I drag an event (make an edit) and try to re-load the change I get the following assert (Debug / MSVC):

history_edit_error.mp4

good catch, weird the crash only occurs on msvc.

fix pushed -> 7c3fd05

[cklosters]

Thanks for the clarification @TimGroeneboom, this PR will be part of the 0.7.5 release and can be merged into main when the builds pass.

[cklosters]

Merci! feel free to delete branch if you don't need it anymore.