When uploading form sometimes it is desirable to change the name of the file, specially when the filename has some issues (already taken, contains illegal characters etc).
- Add new filename in metadata section
- New field is mandatory
- When selecting file, copy filename to filename section
- If filename is illegal, normalize it to something that is ok (use something like CourseEditorHelper.createUniqueRelFilePathFromShortTitle())
- Tell user that name has been modified due to illegal characters in GUI
AND: fix wrong title in upload dialog...