fix problematic and unnecessary id collision
update conversion of OBO alternate identifiers

as discussed in
https://github.com/owlcs/owlapi/issues/317#issuecomment-67412550
Test case for alternate identifiers
improve conversion from OWL to OBO, add test case
Use IRIs for replacedBy
improve owl2obo roundtrip

preserve unexpected annotations on alt id entities as untranslatable
axioms, includes test case