File browser can receive directory metadata.

Added logic to the client-side file browser so when it does AJAX
requests for directory data it can receive directory metadata and
assign it to its internal representation of the directory.
Directory AJAX feed provides directory metadata.

Updated the AJAX feed for providing SIP arrange directory data
with level of directory metadata.
Display level of description in SIP arrange.

Updated client-side UI logic to display level of description for
directories.