Add a DMaaP simulator

Add a DMaaP simulator

Added a DMaaP simulator for testing applications.  One current
limitation is that the simulator does not support multiple "subscribers"
on the same topic; if someone gets a message, that message cannot be
subsequently retrieved by anyone else.  The simulator has also not been
tested for concurrent getting and posting.

Also added a way to set the response code DMaaP would return for a get
to test that policy can gracefully handle errors.

It may need some work to become truely its own "feature"

Issue-ID: POLICY-489
Change-Id: I524981bdf5e4e825f13e6197dda11d9498e4f4bf
Signed-off-by: Charles Cole <cc847m@att.com>