Add more regression tests

Examples were replaced by tests in #26 

The following additional full application tests should also be added.
- MPI run
- Threaded run
- Hybrid run
- UWUW  dagmc run
- Test outputs? (.e.g. moab full, moab surfs)
- OpenMC performance
- OpenMC direct comparison
- ...?

Delete the following once redundant
- openmc/performance/
- openmc/perf_test.i
- dagmc_uwuw.h5m