sysutils/duplicity: Options update

• Use GNUPG2 as default [1]

• Drop SSH option
  
  Install paramiko and pexpect as SSH/SCP/SFTP backend.
  
  Duplicity uses paramiko as default, and pexpect is necessary for par2backend.py, thats why we are also installing it. [2]
  
  scp:// will use paramiko, you can also set like this paramiko+scp:// or pexpect+scp://

PR: 232927 [1]
Reported by: rs.os@t-online.de [1]
Reported by: Paul Holmanskikh <paul.holmanskikh@gmail.com> [2]