bge py api: raise an overflow exception when assigning a float to a bge object which is out of the float range.
also avoid raising exceptions by ConvertPythonToValue when they will be ignored.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56480 954f8c5b-7b00-dc11-b283-0030488c597c