updated Shell
WIP OpenGL backend implementation
Merge remote-tracking branch 'origin/develop-SN' into develop-JK
Merge remote-tracking branch 'origin/develop-MW' into develop-JK
fixed Specs
fixed Specs, separated Shape/ShapeElement, added Rectangle, Ellipse, Circle
WIP OpenGL renderer
Merge remote-tracking branch 'origin/develop-JK' into develop-SN
openGL draw rectangle
Merge branch 'develop-SN' into develop-MW