MH-9497 -- filter out episodes the caller is not allowed to access from result sets instead of throwing an UnauthorizedException

git-svn-id: http://opencast.jira.com/svn/MH/trunk@13996 e6edf6fb-f266-4316-afb4-e53d95876a76
MH-9498 -- fixed URI rewriter to check for possible null on mediapackage element mimetypes; improved exception handling of EpisodeService

git-svn-id: http://opencast.jira.com/svn/MH/trunk@13997 e6edf6fb-f266-4316-afb4-e53d95876a76