Changes to cvterm, dbxref and project tables

[spficklin]

This issue imported from the Chado v1.4 requested changes google doc:

Changes suggested by Bob MacCallum, VectorBase (population biology browser runs off Chado)

cvterm: Email discussions in March 2012 ("Anyone had any luck loading GAZ->Chado cv tables") suggested adding dbxref_id to cvterm's constraint cvterm_c1 - but looking at our schema changes (from Chado trunk) it seems that we have simply dropped that constraint completely. I'm not sure what caused the change of heart, sorry. This is to accommodate GAZ and other ontologies with multiple terms with the same name (e.g. "London").

dbxref: Also GAZ-related I believe: ALTER TABLE dbxref ALTER COLUMN accession TYPE character varying(1024); Stephen says (04/24/2015). This increase in size for the accession seems reasonable to me. (For the record we will gradually reduce our reliance on GAZ in favour of geometric approaches in Solr. I'm not suggesting the above changes should go into the trunk - I'm just mentioning them for completeness.)

project: ALTER TABLE project ALTER COLUMN description TYPE character varying(4096); Stephen says (04/24/2015). I think all ‘description’ and ‘comment’ fields in all tables should be of type text. Not a character varying. A full (and very short) list of our patches applied to an (old-ish) Chado can be found here.