Added dropwizard-embedded module

This adds the ability to embed Dropwizard in an existing service,
without the requirement of a command line io.dropwizard.Application;
instead using io.dropwizard.embedded.Service.
Added unit tests for dropwizard-embedded
Added unit test for Service in dropwizard-embedded

This commit also enforces minimum test coverage requirements for the
module with Cobertura, so that coverage must be above 80% of
lines/branches.