Encapsulated MetaData members. Added helper functions for common tasks.

The common::Clock is supposed to be a 1970 epoch, right? So this fails if the local system has 1970-00-00 00:00:00 when the MetaData element is created. This seems unlikely because the clock would have to be reset at the same time this test was running. I will remove if desired; its not a guaranteed to pass test case.