Add views and templates to bring more user/groups admin within OpenREM

[Ed McDonagh]

Currently users must be added and allocated groups within the admin interface, which is active by default in OpenREM installations, but apart from users using the built-in web server it won't look pretty, as I haven't included any instructions for pointing to the static files etc.

Refs #16 where user authentication was introduced.

[Ed McDonagh]

Added link to user auth in Admin menu. Fixes #259, refs #84. Also added a check to see if there were any users in any groups, and if not, a panel is displayed on the front page alerting the user to this fact and giving the link to the user auth page.

→ <<cset eead0fce16a3>>