Added a debug mode that enables extra logging. MetropolisPlugin.DEBUG
should be true for snapshots and false for release builds.
Added an occupied Plots list to MetropolisPlugin to keep track of both
player homes and reserved plots.
Added the Plot class as a parent of PlayerHome and moved relevant code
to it.
Added a command to reserve plots that aren't tied to a player. This
can be used to setup a larger protected area around spawn