A Wiki::Toolkit plugin to manage co-ordinate data

 Access to and calculations using co-ordinate metadata supplied to a
 Wiki::Toolkit wiki when writing a node.
 .
 Note: This is read-only access. If you want to write to a node's
 metadata, you need to do it using the write_node method of
 Wiki::Toolkit.
 .
 We assume that the points are located on a flat, square grid with unit
 squares of side 1 metre.