changes to explicitly advance the modals after google oauth credentials ...

...are received and to completely remove the problematic connecting state #1841

A good chunk of this diff is the byproduct of cleaning up unused arguments to constructors...will comment.
Removing XmppHandler here was just a cleanup since it's no longer used. Doing so, however, seems to have screwed up Guice's ability to auto-wire everything and led to the creation of the new RosterHandler interface and associated changes where everything references that instead of Roster directly. This keep cropping up, though, so it'll be a useful change going forward.