Limit kit selection

[Palmidence]

Describe the feature you'd like
Allow for an attribute in the JSON of a map to limit the number of players choosing a class/kit.

Usefulness of the feature
If we're looking into implementing kits on public (as we've brushed over several times), one of the ways to reduce the number of players using overpowered kits and to increase the cohesion of teamwork with various kits would be to allow a certain percentage or amount of players restricted to pick that class. See PGMDev/PGM#800 for the idea.

Additional context
max: 12, max: 15%

P.S - What made this server different from all the others was kits. Let's do kits again