now_timestamp is the 0 time of all files and it's used in substitution
of file_stamp for congruence
modified the doc string of now_timestamp function
save the dic_state after the actions delete, move and copy
modified timestamp in inner test function _create_file for congruence
modified expected type for the timestamp
TestUserdataConsistence seems more like a mini system test instead of unittest.
modified to check userdata consistency after move,delete and copy