gre.dump_resource(
    pool_name,
    resource_name
)
		    This function performs the opposite of the gre.load_resource
                        call and removes a resource from the specified resource pool cache.
This call can only be made from the main Lua action execution thread.
Parameters:
            pool_name       The name of the resource pool: image or font
            resource_name   The name of the resource that is to be removed
Example:
		    
-- Force the tree.jpg image out of the cache, image will reload as required
function flush_tree_image()
    gre.dump_resource("image", "images/tree.jpg")
    gre.dump_resource("font", "fonts/DejaVu.ttf:18")
end