Fix dependency issues with hamcrest

Motivation:

We use 3 (!) libraries to build mock objects - easymock, mockito, jmock.
Mockito and jMock pulls in the different versions of Hamcrest, and it
conflicts with the version pulled by jUnit.

Modifications:

- Replace mockito-all with mockito-core to avoid pulling in outdated
  jUnit and Hamcrest
- Exclude junit-dep when pulling in jmock-junit4, because it pulls an
  outdated Hamcrest version
- Pull in the hamcrest-library version used by jUnit explicitly

Result:

No more dependency hell that results in NoSuchMethodError during the
tests