Moving the UD fields over to a new model in memberships.
Resolve migration dependency issue for memberships and directories.
Set admin-only to true for some fields.
Integrate MembershipDemographic into membership add and preview.
Clean up MembershipDefault2Form.
Ensure unselected checkboxes unchecked.
Change the default widget to TextInput for demographic ud fields
Incorporate demographics fields into membership admin backend.
Merge branch 'refs/heads/membership_demographics'

Conflicts:
	tendenci/addons/memberships/views.py