PCA Plots 0.1.1 (resizing and per-plot game modes)

New

• Resize a plot: /plot admin resize <owner> <size>. The plot moves to a free spot of the new size (plots can't grow into their neighbours) and starts empty; the old spot is cleared. Owner, helpers and settings stay the same.
• Game mode per plot: /plot admin mode <owner|all> <adventure|creative|survival|default>. Students switch to that mode while they stand in the plot, and back to the plot world's usual mode when they step out. Used by the new PCA Puzzle Plots add-on to put puzzle plots in adventure mode.

Changed

• A plot with its own game mode can only be changed by someone standing in it, in that mode. That stops a student in creative on the road from reaching in and breaking through a puzzle's walls.