TVPaint: Option to stop timer on application exit.

[tokejepsen]

Stop the timer when exiting TVPaint.

Depends on #1886 and ynput/avalon-core#358

[mkolar]

This is quite dangerous to drop globally as it can easily turn off timers that the user would prefer to keep running. We'd be happy to merge this in, but it needs to be made optional in the studio settings, otherwise, it would affect production too much.

[tokejepsen]

Good point! Have updated so it respects a setting called Stop timer on application exit.

[tokejepsen]

This is ready to go now.