Upload server: implement queue/rounds mini-RFC, misc fixes

[strohel]

Implements the upload server part of #42 + some misc fixes (see individual commits).

@PabloMansanet please feel free to take this over.

What is left to implement is the game engine side: determining round number on startup, maintaining, incrementing and showing round number, writing round-finished.marker file before showing the victory screen, refreshing players for the new round.

[PabloMansanet]

Looks very good @strohel ! I've added a few commits at the end that address the missing parts you described. I've tested this locally and it seems to work well WRT folders and rotation. We really are getting event-ready! :)

[bschwind]

@strohel @PabloMansanet this is needed before the event, right? What more work do we need to do to get this finished?

[PabloMansanet]

@bschwind the only reason I was procrastinating on merging this is that it makes testing locally a bit more difficult (as you need to track the rounds which are a bit of a moving target) but it looks safe to merge before our dry run / sample test. We can always refactor later, but it works well now :)

[strohel]

@bschwind @PabloMansanet this is needed before the event, right?

Yup!

What more work do we need to do to get this finished?

AFAICs the last thing left is your concern that fs access is getting viral and that we should abstract it to own module - we need to decide if we need to do that in this PR, or keep it for a separate one (I'd be okay with that).

[PabloMansanet]

I'd keep it to a separate one, personally: there's limited time we can spend on this codebase before the event and it feels more impactful to spend it in other areas, such as fixing the sound and solving any problems that come up in the test :)

[bschwind]

Sounds good to me, I'll leave it to you two to decide when exactly you want to merge it.