Update to display if the user id is HUID or XID

Summary of changes:
(1) InTemplate: add check for HUID, if user id is numeric and length is 8, then user id is HUID, else user id is XID
(2) In aptags.py:  add new method (is_huid), to check for  if value is numeric and length is 8, return true; else return false
(3) In test_aptags.py: add new test cases for above method
I don't see a test that exercises the exception. If you try to pass in a dict or a list or something other than a string it should throw an exception and return False.