FOR DISCUSSION: Using coroutines for login

[psh]

I split the NetworkingModule into 3 parts with the idea that as classes migrate to use coroutines they will move from one module to the other.

1. NetworkingModule with common stuff that wont be changing (gson, cookie store, client classes, etc)
2. RxJavaApiModule for API interfaces that still use RxJava
3. ApiModule for API interfaces that run using coroutines

Since suspend functions need to be called from a coroutine (or another suspend function) and I cant just convert the LoginActivity from Java to Kotlin, I introduced a view model. The LoginViewModel gives us a neat viewmodelScope to run suspend functions from, and is easily created and called from Java code. (Google's view models will also survive config change too, so we should definitely look at adopting them to deal with the myriad of other related bugs)

All of that is the support ready for the real change of moving to coroutines. Check out the LoginClient and LoginInterface for making API calls.