Support recursive listing/deletes on vsftpd

[robinrodricks]

FTP Server OS: Unix
FTP Server Type: Vsftpd

Vsftpd sometimes supports recursion if enabled. We should take advantage of this as it would give a major performance boost.

From its manpage:

• ls_recurse_enable - When enabled, this setting will allow the use of "ls -R". This is a minor security risk, because a ls -R at the top level of a large site may consume a lot of resources.
  Default: NO

[FanDjango]

I moved this to the Future Plans list in the WIki.