mail_addr field [split from (HowTo) Replace courier with dovecot]

[joximu]

Hi

the mail_id has to be patch into the passwd-plugin - but there are more things to change.

With the mail_address field thing would be *far* easier.

I'd suggest: make use of mail_address and then we can provide a webmail including password change (then the idea of including squirrel with ispCP makes (little) more sense...)

/J
PS: Sure I can commit this into the trunk... when it's ready..