added a new sample "ClockOpenGL" which references the OpenTK project tha...

...t you should get from github!

somehow needed to change some enums in OpenGL. using the more generic namespace OpenTK.Graphics.OpenGL rather than a specific version.
outcommented the font rendering in clock sample for now.

still not so sure about how the textures need to be renderer and how to implement the missing pieces "MyShapeStore", "MyOpenGlTexture", "MyOpenGLRenderProvider" that i needed to declare.