Add simple java maven archetype

Credit to @nicktelford for the majority of this work and @parichards for pairing on this.  See https://github.com/dropwizard/dropwizard/pull/156 for all of Nick's hard work.  I tried to rebase Nick's branch on master, but it didn't seem worth the effort.  

Differences from Nick's branch:
- Shaded by default.  It seemed appropriate that the default should be a shaded jar since the docs and example app show a shaded JAR.
- Fixed a small bug where the main class still had *Service instead of *Application as the suffix.