Add vmail command for changing password when you know the current password
Not 100% sure if this the best way, but the members portal was tied to
*the* mail node, which is not good to begin with, and breaks when
there are multiple mail nodes.
* Replaces vmailpasswd.c, which is an awful program (passed password on
the command line revealing it to `ps' and only supports a local
filesystem userdb).
* Restricted to users with the priv `vmail' for now, and only used by
the portal. Not much worth in exposing generally it seems (vmail
users cannot login to any shell machines, at least at hcoop)
* Includes helper python program to run crypt() (better than C at
least...)
* New function to parse the userdb into a StringMap (a better
approach is possible, similar to the Vmail.list). Will be used to
compile the database for Dovecot later.
* New binary `domtool-portal' to expose replacement vmailpasswd command