Plan geometry

Basic primitive of plan geometry in TiledLand.

Experiements on Convexly...

The main idea was to test Convexly (based on libGEOS) but several conclusion :

• Not well documented : it is hard to do find how to do things : i.e. change Point coordinate for instance...
• Strangely managed Object, so it is not possible to apply hineritance, and so on
• As a result, my strategy to bypass the limitation go on re-instanciate objects, but with a huge cost on the code efficiency...

The test is saved on the test-shapely branch and match the v0.1.0 version.