jacoco for unit test coverage

[nenick]

This works not out of the box but workaround can be found at https://code.google.com/p/android/issues/detail?id=144664

[vanniktech]

I've also been able to finally get Unit Test Coverage reports using JaCoCo. Here is how I made it.

[nenick]

Nice work I will compare it with https://github.com/nenick/android-gradle-template/blob/master/App/build.gradle and take the best of both :)