Recode old MCNext from scratch

[macintoshhelper]

So, I've coded around 90% of the old server already, but I feel that the code is not production ready and that in terms of future proofing, scaling and making the server the best that it can be, it should be recoded from scratch.

Aims of the recode:

• Switch to SpongePowered API
  • Nicer API, less need for NMS
  • Future proof
• Use purer functions and avoid mutating - try to keep mutating code together and coherent