The new challenge selection system stores only one instance of each
challenge, instead of creating new ones when the next challenge is
selected. In addition to that, challenge data is now reset every time
the challenge ends to be able to reuse the same resources.
In a future commit, I might as well only generate the spawnpoints once
in an attempt to make things as quick as possible. The new system may have
some bugs, since it's not fully tested with QA yet.
a714144159