Add keyboard and mouse input handlers and InputCapability, to support passing mouse and keyboard events to embedded rendering systems
Support InputCapability in Qt viewer backend
Add support for mouse and keyboard events in gloperate-osg
Add keyboard and mouse constants (key codes are equal to GLFW)
Use virtual keyboard and mouse enums
Pass on keyboard events in Qt viewer, add test to OsgPainter by adding a StatsHandler (key 's')
Implement handling of keyboard and mouse events in GLFW viewer
Clean up debug code for input functionality (closes #15)
Fix c-style casts
Use ref_ptr for embedded window (not really necessary, but better style)
Merge pull request #19 from hpicgs/input

Basic input handling