Implement map rotation group

[Bamcane]

teeworlds/teeworlds#3289 is useful for our project.

I would like to implement that when I have time to code for it.

[Bamcane]

@tauchyon said that he would work on this feature.

[tauchyon]

@tauchyon said that he would work on this feature.

I'm afraid I can't complete this
My production environment (Win/MSVC) cannot build teeworlds successfully
I spend sometime to trace the problem but still can't locate the excact issue

[Bamcane]

Don't worry, if you couldn't, I would :3