[Geo API #643] Added support for GeoJSON Polygon type - supports only simple filled polygon, and supports saving entities only (not querying).
[Geo API #643] Added tests to ensure that when you've saved Point, LineString and the simple Polygon that you can then get them back out of the database again in the right shape.
[Geo API #643] Corrected the polygon test so that now it checks the structure of the GeoJSON is what it really should look like.  As a result, the extra level of data nesting required provoked a rethink of the storage structure for coordinates so now they're in quite nasty nested Lists, but it makes the equals/hashcode/toString easier and serialises and deserialises in the expected way.
[Geo API #643] Added support for more complex polygons (multi ring polygons), the simplest way possible.
[Geo API #643] Added a polygon interface so that the different types of polygons still look like polygons