Moved some example code out from /src and /tests into /examples/src and examples/test

We discussed a new layout for example and testproject code on the list:

https://groups.google.com/forum/#!topic/pants-devel/cLsY7ksLoyM

This patch covers moving the java examples.  If we like this, I'll continue on with non-java targets and
testprojects into a new /testprojects/ top level directory.

Testing Done:
Updated tests, ran tests. CI is baking.

Bugs closed: 472

Reviewed at https://rbcommons.com/s/twitter/r/868/