ncftp: 3.2.4 -> 3.2.5

Also, add missing ncurses buildInput and add/update meta attributes. The
homepage is back up!
duplicity: 0.6.20 -> 0.6.21

Update to latest stable release. See changelog:

http://duplicity.nongnu.org/CHANGELOG
duplicity: add dependency on ncftp (makes ftp:// work)

ncftp increases the closure size with 5 MiB. Now it is at 310 MiB.