Sync critical TBB prefs with Torbutton
I probably shouldn't just leave non-TBB Torbutton users to fall on their swords. Before the next release, I probably should set dom.indexedDB.enabled and network.websockets.enabled to false, to prevent identifier crossover and DNS leakage.
Though, it's not clear that Torbutton users can always properly disable plugins either, so perhaps this is moot... Still, it's easy enough, so why not?