0025973: Visualization, TKOpenGl - support EAGLContext as alternative to NSOpenGLContext

0025973: Visualization, TKOpenGl - support EAGLContext as alternative to NSOpenGLContext

OpenGl_FrameBuffer::InitWithRB() - add method to initialize FBO with Render Buffer Objects.
OpenGl_FrameBuffer::InitWrapper() - add new method to initialize FBO from currently bound in context.

Aspect_RenderingContext - define type explicitly to EAGLContext* / NSOpenGLContext* for ARC.
OpenGl_Window - allow initialization from alien context for OS X / iOS.