Redo how position cards are displayed

[tmwbook]

In the ifcweb/views.py we determine which positions are shown. The way we do it now is very hacky. We can probably make it less hacky by filtering users based off of the chair and exec permission groups. Then we just need someplace to store the desired order.

[tmwbook]

Ideas for ordering:

• List of string in settings
• Have the query be sorted by name or a custom manager
• Make a model or mixin that would store an order

[tmwbook]

I think we are going to switch over to having a model instead of using permission groups. That solves this problem pretty straightforward