The interface provided by octtree implementations that distinguish between
static (immovable) and dynamic (movable) objects.

@param The precise type of octtree members.
@author Mark Raynsford

Insert the object item into the octtree. 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.