v2.3.26

Conflicts:
	VirtualRobot/Visualization/CoinVisualization/CoinVisualization.cpp

BoundingBox toXML

Fix bug with cloneUniteSubset() where sensors attached to a robot node without a child node would get lost

Switching to NDEBUG preprocessor define
Tidy up cmake files
Remove some unnecessary checks

played around with some coin3d related settings to fix black-screen offscreen render bug
convenient init method

Removed some warnings on windows.

Conflicts:
	VirtualRobot/Visualization/CoinVisualization/CoinVisualizationFactory.cpp

removed renderOffscreen and get focal length