SLING-2827 :  discovery.impl: a resource based implementation of the discovery.api . Committed initial contribution from Stefan Egli (md5: d8891e5401114b2a629d3ff01044a1d6)

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1470424 13f79535-47bb-0310-9956-ffa450edef68