Allow users to include/exclude arguments for F() (RFC 6056 algorithm 3)

[ydahhrk]

Branched off #175. See comments 3, 4 and 5 for details.

This is a new feature, but it's small enough that it should only increase the revision number. Otherwise it'll take a long while to see the light.

[ydahhrk]

@toreanderson: I tested the arguments are included and excluded properly, but didn't actually run FTP through it. Mind testing this?

sudo jool --f-args 10

10 is binary 1010 (both addresses, none of the ports). See jool --help or just jool.

[toreanderson]

It works perfectly! :-)