SLING-3056 : eclipse-m2e-ui plugin and m2e-feature added, resulting from a separation of m2eclipse dependent code from the slingclipse plugins and features. This adds a new feature to the p2update config too.

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1522611 13f79535-47bb-0310-9956-ffa450edef68