Feature for 0.8: Add Mapvotes at the end of a game

[AssassinTee]

After playing teeworlds for a long time people keep playing the same map (ctf5/ctf4_old) all time over and over again. So it might be a good idea to add a mapvote at the end of the game where people can choose form a list of maps the next one to play on.

A lot of games do this already like CS:GO:

This would hopefully make people play the same two maps over and over again. We currently have a maprotation, which is fine, but nobody uses it.

[oy]

Doesn't necessary has to be for 0.8 though.