OsgRenderStage: Add InputSlot for AbstractViewCapability, remove setViewport function
OsgRenderStage: Add functions to handle viewport change and post-OSG-rendering callback
Add OsgFboRenderStage to render an OSG scene into an FBO and convert the textures for usage in a gloperate pipeline
Add method to access the VAO of a ScreenAlignedQuad
Merge branch 'master' of https://github.com/hpicgs/gloperate