IDE support

I created an [Android Studo plugin](https://github.com/evant/android-studio-unit-test-plugin) which requires a gradle plugin to provide a model for the ide to read. I don't expect you to merge this pull request as-is because it dependes on a local library that provides the interface between the plugin and the ide. This [library](https://github.com/evant/android-studio-unit-test-plugin/tree/master/android-unit-test-model) needs to be hosted seperatly on maven central so that the gradle plugin can be updated independently. I'm not sure if you want to pull this in and maintain it yourself, or have me do it.
Add dependency on model shared between the plugin and the ide. This only includes a couple of interfaces and a couple of simple implementations. This needs to be hosted separately on maven central.