WIP: Start on LiveSplit Server Protocol

[AlexKnauth]

I wonder if we could somehow unify both protocols (as in the new one is v2 or so and it gets negotiated)

would it work like... in livesplit-core server protocol, having it try to parse it as JSON, but when that fails, fall back on a different parser that recognizes the same protocol as normal LiveSplit?
and in normal LiveSplit, something similar, recognizing commands in either format?

possibly

A WIP incomplete translation from LiveSplit/src/LiveSplit.Core/Server/CommandServer.cs.

Currently untested, and the main client I plan to test it with will only exercise a couple commands, not everything.

Missing these commands entirely:

• addloadingtimes
• alwayspausegametime
• setsplitname / setcurrentsplitname