Further renaming for consistency
Removed RobolectricTestRunner from DependencyResolver methods

Moved the configureMaven() method from RobolectricTestRunner to
MavenDependencyResolver, since it is only applicable there. This
means that DependencyResolver methods no longer require an
instance of RobolectricTestRunner.

THIS IS AN API-BREAKING CHANGE.

Instead of sub-classing RobolectricTestRunner to provide custom
Maven configuration, it is now necessary to subclass
MavenDependencyResolver.