INT-3172 Add Recursion to LS/MGET

INT-3172 (S)FTP - Add Recursion Option to LS Cmd
    
When recursing, the returned filenames are relative to
the top level directory.

INT-3172 (S)FTP - Add Recursion to MGET Command
    
https://jira.springsource.org/browse/INT-3172