use android model instead of custom one to pass info to IDE plugin

This requires an update to the android studio plugin as well, (which I have already [completed](https://github.com/evant/android-studio-unit-test-plugin/tree/android-model)). Currently, this change keeps the old way of doing things around for backwards compatibility, but I don't know if that's the best option.

1) We don't worry about backwards compatibility, you have to update both the gradle and AS plugin and the same time.
2) Keep backwards compatibility in the gradle plugin.
3) Keep backwards compatibility in the AS plugin (currently not implemented but would be easy enough to do)
4) both 2 & 3.
Can we keep this space?