Migrate away from flag-based commands to autocomplete

[WizardCM]

While the flag-based command system is neat, it ends up being more confusing than anything. With autocomplete it's much easier to have a better idea of what a command's parameters are and to submit them.

[BlaneyXYZ]

Commands that still use Flags

/firework this one may keep flags (could maybe use some GUI)
-fade
-power
-color
-shape
-flicker
-trail

/item
-name
-lore

/worldmanager
-name
-eject