Add explicit org.hamcrest dependency

org.mockito is pulling in hamcrest-core 1.1 while junit requires 1.3.
This results in failures when the two meet, for example in yangtools.

Change-Id: I4040d712f939aad698a45fca45c727918524578f
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "Add explicit org.hamcrest dependency"