Updated entity.FORMAT_CHOICES vocab
display master/mezzanine files in tabs on entity-detail page
change order of display fields on file-detail; mv xmp down

When there is XMP at all it's often a huge blob of XML that
most users won't want to look at.
Merge branch 'master' into celery-notifications

Conflicts:
	ddrlocal/ddrlocal/templates/base.html
	ddrlocal/webui/templates/webui/entities/detail.html
keep task status msgs in one place; show statuses for diff actions

First implementation was pretty much hard-coded to only show
file uploads, and messages were constructed in the page template.
With this commit,
- Messages are collected in a dictionary
  by Celery action (ex: 'webui-file-new-master', 'git-sync')
  and by status ('PENDING', 'SUCCESS', 'FAILURE', etc).
- Message arguments are taken from the fields in the task dicts.
- Messages are formatted and then added to the task dicts, after
  which they can be displayed in templates, etc.