Timeline: Tweak crossfade appearance.
Timeline: Fix peak display while recording.
Timeline: Add freewheel button.
Mixer: Clean up some issues with display of JACK connection lists.
Mixer: Don't process (dis)connection notifications from JACK while destroying chain.
NSM/jackpatch: Rebuild patch network upon NSM save.
NSM: Command all unneeded 'switch' capable clients to exit when switching sessions.

Closes #60.