SLING-4162 Introduce "OsgiContext" junit rule for OSGi and OsgiContextImpl

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1639589 13f79535-47bb-0310-9956-ffa450edef68
SLING-4162 fix javadoc

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1639590 13f79535-47bb-0310-9956-ffa450edef68