Cleanup/rename richards tests

Be aware that the parallel tests failed for me, but also fail when I do that with master (No such file s-0002*.pvtu. )Someone needs to make sure they actually pass on a different machine.

The following tests FAILED: 3 - test_richards_box_parallel_yasp (Failed) 4 - test_richards_tpfa_parallel_yasp (Failed) 5 - test_richards_tpfa_parallel_yasp_restart (Failed) 6 - test_richards_box_parallel_ug (Failed) 7 - test_richards_tpfa_parallel_ug (Failed) 8 - test_richards_box_parallel_alu (Failed) 9 - test_richards_tpfa_parallel_alu (Failed)