[WIP] Adminpanel

so far
- [x] add .admin method to Person model
- [x] make a dashboard index view that displays the current admins
- [x] make changes to the user menu, so that admins can access the dashboard
- [x] add random gif
- [x] possibility to make and unmake admins from the dashboard
- [x] blog administration

next steps, **edit: moved to another issue**
- [ ] possibility to make and unmake admins from the person views
- [ ] possibility to delete groups and users from the dashboard and the corresponding views


questions:
what tests do I need? and *where* do I need to put them?
**Edit: added all the tests**
closes #240 #243 #196 #194