Metadata Schema: Let's Break Everything

Big changes:

* CKAN tags field is no longer used.  Free-form keywords are now stored in 'keywords' and 'keywords_fra' fields instead: comma-separated tag names, *not yet cleaned/validated* or converted to tags for solr
* date_published is now a normal user-editable field
* portal_release_date is the new admin-only field that controls publishing
* name field type changed from 'slug' to 'calculated', but the value of this field is *not yet actually generated* so it still needs to appear in the form.