tgon/tgoff commands to turn on/off messages, jdbc integration to store players, refactoring

[elvyyy]

I decided to make tgon/tgoff commands, also to integrate with Hibernate and a database.

All changes have been made for my own needs, but I hope some of them could be useful :-)

[mastercake10]

Thanks for your PR. I have never really looked into this Hibernate thingy, but is it really needed for a project this size? It seems like it introduces a few new libraries too, like the javassist lib, xml libs etc. I don't understand why it needs Javassist, Hibernate should only alter existing fields but isn't expected to compile new classes at runtime, right?

Currently, the jar with all dependencies has a size of ~17 MiB. That's far too big for a simple MC plugin imho. All other changes are fine.