Performance on metadata view is too slow

URI Resolver are used too often to query the same information. Complex information is retrieved where only simple questions should be answered, e.g. "Is the mainFile of derivate X a PDF document?" This resolves currently in this information flow:

1. retrieve derivate XML

2. get main document

3. get file listing of all files in the directory where maindoc is laying

4. extract the file information regarding maindoc

This bug is to track the progress on fixing performance issues on metadata view.