Auto-assign tabs to a group

[adipose]

Autogroup is an extension that used to work with Panorama, and now works with Tab Groups extension. Due to the fact that Tab Groups is not going to be supported in the future (and already doesn't support e10s), Autogroup functionality would be great to bake into Simplified Tab Groups.

All that is really needed is auto-assignment based on regular expressions. The work was done with Autogroup, but since it was designed to be compatible with a different extension, it might not be that useful.