Removed URLs from thumbnail generator. Removed learning object description from bitstream. Calling chmod on uploaded file.

Fixed temp download file permissions. Fixed learning object importer link. Fixed dspace upload mimetype nil exception

Ensuring the databse connections are cleared once workers are done. Redirecting download to uploaded files while DSpace upload is not finished.

modified the column type LearningObject id (int->str) to DSpace 6.3 and download system ( retrieve link)