SLING-4182 Downgrade Sling API dependencies to the minimum required API (2.4 instead of 2.8)

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1642292 13f79535-47bb-0310-9956-ffa450edef68
SLING-4209 Expose required JavaScript files through the BundleResourceProvider

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1642293 13f79535-47bb-0310-9956-ffa450edef68