fixed small bug
added configuration to DepthPacketProcessor, right now just allows to set min and max depth
added options to enable/disable the filters to DephPacketProcessor::Config
added glfw and glew as dependencies; implemented basic opengl window display;
increased opengl version to 3.3
implemented gpu depth processing using opengl shaders
shortened image format definitions
removed opencv dependency from OpenGLDepthPacketProcessor
OpenGLDepthPacketProcessor now uses its configuration
Merge branch 'opengl_depth_processor' of https://github.com/christiankerl/libfreenect2 into opengl_depth_processor

Conflicts:
	examples/protonect/include/libfreenect2/depth_packet_processor.h
	examples/protonect/src/opengl_depth_packet_processor.cpp