Add 'ontology' selection for remove and filter

[beckyjackson]

To remove or filter for the ontology annotations:

robot filter --input x.owl --select ontology --output y.owl

Returns a new ontology with only the ontology annotations from x.owl

robot remove --input x.owl --select ontology --output y.owl

Returns a copy of x.owl without any ontology annotations.

See #451

[matentzn]

Just to be annoying (sorry):

robot filter --input x.owl --select ontology --term-file terms.txt --trim false --output y.owl

Returns a new ontology y with the ontology annotations from x.owl and all axioms containing terms in terms.txt?

[beckyjackson]

No worries. Yes, that is correct!

[jamesaoverton]

I think this is right. It has always bugged me that "imports" is handled in a special way, and now "ontology" is handled in a special way, but I don't see an alternative.

Please include a test that addresses @matentzn's specific use case.

[beckyjackson]

Side note, @matentzn - I would also add the annotations selector to that command to make sure any classes that get pulled in as a result of the filter have labels, etc (otherwise they will only have the declarations).

[matentzn]

Thanks @rctauber!