add API to measure the dimensions of an object

useful for debug purposes and to build the bounding box
of an object.
add API to build the bounding box of an object
add option and code to handle the bounding box

optionally draw the bounding box of the loaded model.
still too much static.
add utils: to inspect the properties of a model

inspect the properties of any supported model
without actually render it.
more stuff to do.