Support passing through XML extensions in getRecordings

Recording processing scripts can now add arbitrary XML elements in
the extensions section of the metadata.xml file, and those
element will be copied to the getRecordings XML response.
minor fixes to bbb-conf
Merge pull request #322 from kepstin/tomcat-recording-extensions

Support passing through XML extensions in getRecordings
 - fix race condition on create and join api call
Merge branch 'merge-polling-with-master' of github.com:bigbluebutton/bigbluebutton into connect-bbb-apps-html5