Changed module names to lower-case and group to org.opencadc to conform to maven repo naming standards

Story 1869. Updated codes based on Brian's second code review. Mock UserPersistence is still not returning the programmed exception.

Story 1869. Updated code based on Brian's code review comments. A couple of unit tests are still not working. The mockPersistence object does not seem to throw an exception as expected.

Story 1869. Added unit test for the POST operation. Test for the happy paths will be the responsibility of the integration test in ac_ws.

Story 1869. Renamed PasswordServlet to ModifyPasswordServlet. Added unit tests to ModifyPasswordServlet.