Add SlimeLoader#renameWorld

[dementisimus]

This PR allows to rename worlds by SlimeLoader#renameWorld

Redis support will be postponed.

to-do:

• add mongo support
• add mysql support
  (- [ ] add redis support)
• add file support

[dementisimus]

• add redis support

due to some unexpected issues with redis

• java.lang.NoClassDefFoundError: io/netty/resolver/dns/DnsCnameCache
• java.lang.NoSuchMethodError: io.netty.resolver.dns.DnsNameResolverBuilder.socketChannelType(java.lang.Class) (even with 4.1.63.Final)

I won't be adding redis support now. I will be working on fixing this issue with redis. If this issue has been fixed, I will open an additional PR for adding redis support to SlimeLoader#renameWorld.

[Paul19988]

If you do not intend to add Redis support for now, please ensure that it informs the user when attempting to do it whilst using redis (implement an UnsupportedOperationException)