Reorganize bundle directory structure for TBB 3.0

I think our updaters (Thandy and/or Firefox's) and a few other issues (#6457 (moved)) would be simplified if we tried to reorganize our bundle structure a bit so that more of the bundle's executable bits (the parts that need updating) were grouped together with Firefox.

Doing this will require updates to Tor Launcher and the launch script, and probably several config files.

Of course, this might not matter for our updater, so maybe we don't care.