Rest removal (#1588, part 1) [WIP]

[aylinni-empyrea]

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• [x] Remove REST from TShock
• [ ] Complete redesigned plugin and add a link for it in changelog (?)

This PR removes all traces of REST from the main codebase, which later will be ported over a separate plugin. (for #1588)

(also removed Group.ParentName as its comment stated it was added for rest, can add it back if need be)

[AxeelAnder]

I'm going to do this for current httpserver lib is not .netstd.

[hakusaro]

I suspect this won't get completed. If it will, please re-open.

[QuiCM]

I suspect this won't get completed. If it will, please re-open.

I intend to do this with the DI refactor & uplift to .NET hosted services. Happy for this to remain closed