Sequence property was hidden. According to translation rule it now
changed on self.CHARACTER_CLASSES_CLASS property.
As result code in validation and handle_create methods can be removed.
Also unittests was changed to demostrate changes applied for Hidden
property.
Class with TestGenerateRandomString was changed to use new algorithm for
generation random strings.
Change-Id: I3f81df94b24e0f751d2070dc314f15ceb95164ce