Make enum's static. The are implicitly static anyway, but this...

makes this explicit.
Going to try using Calendar instances on DomainObjects.

Previously we just copped out and used the raw string values, so this
adds a utility helper for parsing, serializaing Calendar instances to
appropriate format strings.
Allow CalendarUtils to handle times without fractional seconds.
Added convenience method to explicitly generate activation code.

Just calls the other hmac methods, but this makes calling the method
more memorable.
WIP - add devices. Not sure about the API yet.

Curently published methods on device are get, update, delet and
activate.