Better support for multiple departments

[dpausp]

Support for multiple departments is incomplete in some parts of the application. Find out what is still missing, including:

• permissions for department admins: functionality may be limited to global admins at the moment

• permissions for normal users:

  • voting for arguments must be limited to department members
  • adding arguments in other departments should be optional

• as user, I want to find out which departments I am a department admin for (add the info to the profile page)

• propositions should show which department they belong to. It's only visible indirectly by clicking on the ballot, but that doesn't work for drafts.

• the department page should have links for common use cases, like seeing drafts, all propositions (with or without drafts?), current voting phases and historical voting phases (needs voting phase filters) => Public/personalized department overview #92

• as normal user, I want to see

  • my departments first on the department page
  • voting phases for my departments first on the voting phase page
  • propositions for my departments (add a proposition filter)

• as a department admin, I want to

  • add propositions as submitted, skipping the draft phase

• look at tests for all affected views and implement permission checks: as normal user, as department admin, as global admin