BibDocFile: convert files and icons asynchronously
- When uploading files via the document file manager interface, do not attempt at creating other formats and icons immediately, but delay their creation via the use of dedicated tasklets, in order to reduce the waiting time on the user's side. (closes #1428)
- Introduces parameter 'deferRelatedFormatsCreation' in Create_Upload_Files_Interface WebSubmit function to fall back to previous behaviour if "related formats" creation should happen immediately.
Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>