PlotRand

Adds bStats metrics and fixes a set of issues found while reviewing the whole plugin.

Fixed

• Merged plots could get a border drawn across a neighbour's plot. The ring followed the bounding box of the merge, and on a merge that is not rectangular that box reaches into the plot sitting in the gap. The border now follows the outline of the claimed area itself, with the seams between joined sub-plots left out.
• Blocks are placed without physics updates, so a ring of several hundred blocks no longer sets off falling sand, redstone or water along the plot edge.
• Restoring the original blocks now finishes before the stored data is dropped. A block type removed by a Minecraft update used to leave the border standing with its originals already deleted.
• A plot world whose name contains a dot lost its stored blocks on restart, leaving a border that could never be removed.
• A malformed line in the data file no longer stops the plugin from starting; it is skipped with a warning.
• The border height is checked against the world before anything is placed.
• Dragging items in the menu is blocked, not just clicking.

Added

• bStats metrics.
• Styles are validated when the config loads. A material that cannot be placed as a block or drawn in the menu, a slot the menu cannot reach, or a slot another style already claimed is skipped with the reason written to the console, instead of failing halfway through building a border.

Changed

• The state file is written asynchronously instead of on the main thread.
• Only the plot outline is walked rather than its whole area, so the work scales with the edge length instead of the plot size.
• The cooldown covers removing a border as well, and only starts once something actually changed.