Updated authentication methods to login v2

@katowulf - Please review but **do not merge**. I want to get your thoughts on everything up to this point. There is still more work to be done here: testing (I am going to need to updated `mockfirebase` first...), removing Simple Login code, taking authentication out of this user management file, etc. Please provide any feedback on how things are structured though.
I would prefer to see $firebaseUser as this is the convention we've adopted thus far. Alternately, we could break everything and rename the $firebase objects. But it's not great to have everything else prefixed $firebase except for this service.