Revert my previous ITriangleSelector patch and implement garritg's great idea about retrieving an ISceneNode by index.  Add an out parameter to ISceneCollisionManager::getCollisionPoint() to return the hit scene node.  This is an API breaking change; the test and example apps have been updated.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2125 dfc29bdd-3216-0410-991c-e03cc46cb475