bug fix of RANDOM button

Gamemode name conversion is now server-sided, improved code readability

fixed RANDOM button accidently choosing itself

fixed bug of not changing map when there's no replay button

added more detailed error messages

small tweaks, maybe fixed the maplimit bug?

added skipping mapvote if there's just one map to choose from

added config option to activate/deactivate map previews
fixed config file not working

added map previews

small fixes