Typedefs imported from RO should be refered to using xrefs

[althonos]

Hi!

The OBO semantics describes the following procedure to use local names for RO (and BFO) relationships:

1. Declare a local typedef with an unprefixed ID
2. Add an xref to the actual RO typedef

So for instance the following frame from rnao.obo:

[Typedef]
id: ro.owl#has_quality
name: has quality

should instead be declared

[Typedef]
id: has_quality
xref: RO:has_quality

See the OBO semantics section 5.9.3 and 8.2.2 for more information about this mechanism.