Type_ID fields

[spficklin]

This issue is a requirement for alpha1 release. We need a field that can link the entity type to a type_id value in the Chado tables. The end-user should not be allowed to change this value. It's only needed for content types whose type directly maps to a type in Chado.

In contrast, some Chado records may have a type ID (e.g. organism.infraspecific_type) which provide additional context for the record but may not define it as a separate content type.

Perhaps a single field could handle both. Is it possible someone may want content pages on these other types? For example, by organism infraspecific type??