The interface provided by quadtree implementations that distinguish between
static (immovable) and dynamic (movable) objects.
param   The precise type of quadtree members.
author  Mark Raynsford

Insert the object item into the quadtree. The object will be
given the categorization type.

The function returns false if the object could not be
inserted for any reason (perhaps due to being too large).

@param item The object to insert
@param type The categorization of the object
@return true if the object was inserted

Remove all dynamic (movable) objects from the tree.