Replace the usage of mockito-all with mockito-core in the test classpath

ModeShape uses across several of its modules the mockito-all library for mocking in certain tests. However, this library has a transitive dependency towards hamcrest-core which could potentially come in conflict if/when another independent version of hamcrest is used together with junit.

To avoid these potential conflicts, we should replace the usage of mockito-all with mockito-core which doesn't have this transitive dependency.