Handling of obo namespaces in golr loads

Ontologies are not well behaved in populating the obo format 'namespace' tag with meaningful, concise values (important note: obo namespaces != owl/xml namespace. See obo specs).

We should ditch the namespace field in favor of a more useful category field. This would cause a bit of churn. We can instead overload the namespace field and overwrite it with useful info.

Mapping from ID space (CL, GO, etc) to value:

• GO: use existing obo namespace field
• MA: 'mouse anatomy'
• CL: 'cell'
• UBERON: animal anatomy
• EMAP: 'embryonic mouse'
• CHEBI: chemical
• Anything else: uc(IDspace)

last step: s/[\-_]/ /g; (for amigo facet purposes)