initialize the OpenGL context as soon as possible

Change-Id: I58051695d0ca8384fb771bfc74aeb228145f77e6
remove the glew part in OpenGLRender.cxx

The glew init part is now in vcl"s OpenGLContext class.

Change-Id: I423e45cf7297df87cb8668b43f9243589b7e26ff
don't try to init OpenGLRender in the constructor

wait until the context has been created and we can actually render

Change-Id: I841d64ae847a2fdc74954887d3a6fcfcd06fc6a3