Setup a declarative REST testing extension

Convert the RESTEasy extension prototype Aslak created under the Arquillian Showcase into a standalone module.

Tasks:

• Migrate the code from the arquillian-showcase https://github.com/arquillian/arquillian-showcase/tree/master/extensions/resteasy to the new repository
• Change the code to use the JAX-RS 2.0 standard client APIs instead of RESTEasy