Easyblock nwchem

Needed for NWChem version 6.3
Good to hear you dove into these test, I was never able to (I lack the domain knowledge, for one).

Rather than removed these tests for a particular version of NWChem, just removed them all together from the list of tests being run, especially if you have serious doubt whether they ever worked at all.
Just add a comment with a list of names of tests that were omitted because they're known to be broken.
And feel free to reorder the `dirdyvtst/oh3` and `dirdyvtst/h3` tests to make sure they can actually succeed, no need to do that in a separate if clause either...