replace glowutils::Camera with CameraEx in all classes, making it easier to choose the projection type as needed #57

I need this do be able to call Terrain::drawDepthMap with a projective and orthographic Camera. It's not possible/elegant to handle this with a Camera pointer, because the class is not really polymorphic (missing virtual declarations in projection() etc).
render water terrain together with water particles, faking the transformation =) #57
minor fixes #57
different depth map shaders for linearization of projective depth values / pass-through after orthographic projection #57