Add Dropwizard 0.7.0 documentation

Add documentation (user guide and Maven sites) for Dropwizard 0.7.0.

The Maven site for the parent project will be at http://www.dropwizard.io/0.7.0/ and the user guide at http://www.dropwizard.io/0.7.0/docs/

It was generated by running `mvn clean site:site site:stage` from the `v0.7.0` tag after rerverting 985ee4bd091429f4c8f91b0a7e1d442043a43c19.

If you're already on Java 8 you might want to add `-Dadditionalparam=-Xdoclint:none` when rebuilding (or if you want to reproduce the output).