Implement commands for /sgsetup

[spazzylemons]

There is a card for this, but I feel that making an issue for this will make it easier to work on and more visible.

See: https://github.com/DumbDogDiner/StickySurvival/projects/1#card-54973222. Checked items are configuration settings with a complete command that can set them. It also might be worth seeing if some configuration settings are redundant or can be simplified in the process of building these commands (e.g. max players is unnecessary since the max number of players should be the number of spawn points).