Chipmunk2D 7 Support

[jhasse]

Issues of Chipmunk2D which are blocking support for version 7 in Chipmunk++:

• [x] https://github.com/slembcke/Chipmunk2D/issues/90
• [ ] https://github.com/slembcke/Chipmunk2D/issues/104
• [x] https://github.com/slembcke/Chipmunk2D/issues/107

Last working version of Chipmunk++: https://github.com/jhasse/chipmunkpp/tree/v6.2.1

Stuff that needs to be figured out:

• [ ] Replacement for Shape::setGroup
• [ ] Replacement for Shape::setLayers

[jhasse]

Also created a 6.2.x branch now: https://github.com/jhasse/chipmunkpp/tree/6.2.x