Update Readme with better docs

[hakusaro]

I’ve come to the determination that our documentation sucks for developers. In particular:

• Building TShock from scratch is non-trivial, at least on macOS, maybe on Windows.
• Basic system architecture (what files do what and which things operate where) is non-existent.
• The relationship between TShock, Terraria Server API, and OTAPI is not clear.
• What TShock provides as an API to other plugins and what it expects other plugins to reimplement is non-clear.

In addition, I think it’s worth having a quick start guide for how to at least get up and running with TShock in a nutshell. This doesn’t have to be in depth, but it should at least cover starting the server, authenticating, and creating a couple accounts.

RIght now, this is on my todo list for implementation later today.

[QuiCM]

I feel like we should probably blow away much of the current readme documentation because it's all quite old

[hakusaro]

Ya, all on my list c: