+ Returns a tuple with the network identifier and created_items, or raises an exception on error
+ created_items can be None or a dictionary where this method can include key-values that will be passed to
+ the method delete_network. Can be used to store created segments, created l2gw connections, etc.
+ Format is vimconnector dependent, but do not use nested dictionaries and a value of None should be the same
+ as not present.