Adding a basic polygon class

I have added a Polygon class in the basic package. For now this is only working for non-self-intersecting polygons. It can decompose complex, concave polygons into simple convex polygons with an arbitrary amount of edges. This is based on an ear-culling triangulation which can also be done with complex polygons. Additionally there is an convex-hull method implemented, the algorithm is called graham scan.

I started to implement external file import for svg files. At this moment this import graphical content and basically fonts. Styles are ignored completely for now and only the outlines are used.

I am quiet happy about mastering my first remote push with git and will comments to the source code the next days.