Add multi-server support

[JorisvD01]

Hi, I had a very specific usecase for this plugin; We are running multiple servers connected to the same Velocity network, and everything is shared between those servers. Inventory, health, items, and a single Skyblock instance is hosting islands across those servers to reduce and spread load.

We wanted to use Irp on all servers, connected to the same database (so it all feels like the same server). However, all worlds have simular names, so you couldn't tell apart which server a death happened in, so if you tried to visit it the location would not be the same.

With this commit I added part of support to additionally log a servername (configurable in the config). Servernames are shown with the irp's, so you can visually see where it happened. If you try to teleport to one in another server, you will be sent to that server instead. I couldn't figure out a way to TP to the death after you switched servers without the need of some sort of redis / proxy plugin setup, so I figured this was good enough for me.

Feel free to use this, however its not migrating any existing backups yet. We could start with a clean database, so I didn't specifically needed that, and figured if you are not gonne add this (which is understandable) it would be a waste of time. Everything should work as it is now if you are not using a proxy. It'll just always send to the right location.

This also is a solution to Issue #51