changes tags to a list of dicts in the db, adding tag slugs

changes tags to a list of dicts in the db, adding tag slugs

- adds a function to convert the tag list of dicts to a text string
  properly delimited for loading into forms
- tag string conversion function updated to generate list of dicts
- updates all mentions of the conversion of the string to the tags db
  object
- adds a tags template utility and updates the media template accordingly