Separate Mute from Ignore

Currently, when you Mute a track, its silence gets implicitly ignored, and there's no way to turn that off.

This feature would separate these controls, while keeping them working the same way as they currently do.

The idea: when you click Mute, the Ignore button turns on at the same time (so the behavior is the same as today, with the addition that the Ignore button would be lit up). This would let the user un-click the Ignore button if they want to have the track muted for export, but while still paying attention to its silence for the purpose of silence removal.