BIS-753: Working on attaching the DSS widget to a concrete collection/object. Fixed the problem with listing files for an entity that has no folder on the FS.

BIS-753: Merged the changes from master. Using Error objects instead of strings for errors in promises.

BIS-753: Fixed binary data processing for the new DSS widget. Added loading popup for file download.

BIS-753: Added a check when copying/moving files, to make sure that file names do not collide with the existing ones.

SSDM-13579: Fixed infinite refresh issue and the fact that even nested files were shown in the list.