Use jsonapi for map vault, mod vault & player aliases

[Wesmania]

The server uses jsonapi now, and it's about time client started using it. All the pieces for jsonapi are there:

• quamash as a way to do async with qt. This PR is supposed to add some signal stuff to it so we can use it more conveniently, but it seems it can be implemented outside the event loop (I expect the PR to get closed any moment). If so, then we can just add that convenience code from the PR to the client somewhere.
  This branch makes use of quamash with the above PR, it can serve as a sort-of example how to use it.
  I used to be worried about the fact that quamash uses some os-specific things to implement a full event loop, or about potential bugs, but being able to use entire aiohttp is extremely tempting.

• jsonapi-client lets us use jsonapi asynchronously. It's python3.6+, but I can see distros moving away from python3.5 anyway (and it doesn't hurt windows builds). I didn't read into its API much yet, so no examples beyond their docs.

• FAF API documentation.

• OAuth will be necessary at some point - not for things listed in this issue just yet. We'll need to authenticate with player creds to access some endpoints. There's an old prototype branch of the client that might be of use when it comes to using oauth. Of course, if there's some Python library that makes it easier, I'd love to know of it :)

[norraxx]

Some api docs:
https://api.faforever.com/v2/api-docs
https://api.faforever.com/elide/docs