Fixed warnings
Preliminary remapping of internalFormat for GL3 core profile
Merged changes to DisplaySettings from Stephan Huber in prep for controlling the menu hiding behaviour under OSX.

Added new WindowSystemInterface::setDisplaySettings() method to provide a mechanism for passing settings onto the WindowSystemInterface so it can then set up the system appropriately.

Added assignment of the DisplaySettings to the WindowSystemInterface in Viewer/ComppsiteViewer::realize().
Added support for Group::addChild/setChild/getChild/getNumChildren.
Cleaned up addChild/getChild/setChild/getNumChildren methods and added readNodeFile, readImageFile and readObjectFile functions
Merge branch 'master' of https://github.com/openscenegraph/osg into Dev