WorldManager related tasks

[BlaneyXYZ]

permission checks for worldmanager subcommands is misbehaving

/rcmds reload then changes to the worlds.yml get reset

ability to modify worlds.yml using commands

[WizardCM]

On this front,

Turns out the permission issue I had was that I had set rcmds.worldmanager when it should have been rcmds.worldmanager.*. No change needed there.

I've also put a bunch of effort into fixing up the existing WorldManager commands, so it's now at a nicer baseline for future changes.

For the third point, I'm thinking /wm modify <world> <setting> <value/default>.