Move discovery api to a different directory to create a structure as discovery consists of several modules

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1467213 13f79535-47bb-0310-9956-ffa450edef68
Set svn ignore

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1467214 13f79535-47bb-0310-9956-ffa450edef68