First version of template

A preliminary version of with minimal configuration of the menu and the content pages.
Please extend the template when necessary.

See merge request !7

[ci skip]

Add boards

Closes #11

See merge request !6

Closes #11

Closes #12

[ci skip]

Extend committees with extra data

oprichtdatum
einddatum
contactadres

See #11 

See merge request !5

auto_now_add overrides what's set by the user

See #11

Manipulate committees

 Implements: manipulatie memberships fixen
*  if voorzitter verandert moet het een nieuw membership worden en het oude deactiveren.
 *  Verlaten van een commissie moet niet het deleten, maar het inactive maken (misschien maar gewoon met de hand doen though)



See issue #11

See merge request !4

See #11

See #11

Consistently refer to members app by English term

I guess it's clear what happened here.

See merge request !3

Implement a committee-based permission system

Warning: this made a mess of the auth system so I have completely new migrations. Just nuke your database and do `./manage.py migrate` (and `createsuperuser` again.)

See merge request !2

Includes tests and an authentication backend to check the permissions
granted to committees.

Remove reference to mongo backend from CI



See merge request !1