Make RandomLevelsCategory use seed from game

[jvyden]

Closes #122

Why

Previously, we were using a globally shared instance of Random when calculating the random order of levels. This caused levels to appear multiple times in the list and caused others to get potentially missed entirely.

By using a consistent seed we can negate both of those problems and ensure the full list gets hit consistently.

How

To fix, introduce the client's seed parameter as an available parameter to use in the filter settings. We can then use this to create a new Random object on each call of GetRandomLevel() with the new seed.

Remarks

This will require a change in refresh-web to make the website generate a random seed, since if we do not find a seed value server-side we simply use 0.