Test restricted_to dropdown on Readouts; consider exclusion of change etc.
Split into group and restrict; throw exception when restrict but no group
Merge branch 'master' into Issue-#243
Change field name for admin
Make binding to a group mandatory
Make all assay related models restricted
Add fields to admin
No longer need validation error import
Merge branch 'Issue-#243'

Conflicts:
	assays/models.py