Jetty bundled distribution

This PR makes the following changes:

* Add a distribute archive that contains jetty, geoserver and mapfish print so people can easily try out the application
* Change examples sub-project to run, build and test archive
* Remove examples behaviour where it started 2 jetty instances, one for core and one for geoserver in examples, instead the one jetty that is bundled is used for testing.

The build API remains the same except that to run jetty with debug options enabled one can use the `-DdebugJetty` or `-DdebugJettyPort=8000` system parameters (see README.rst for details).