* Add some checks for user name matching in mail user scripts
* Fix user matching problems in mail user scripts
** fix matching problems at several places:
"delmailuser a@example.com" deletes also user "aa@example.com"
"delmailuser a@sub.example.com" deletes also user "a@sub-example.com"
** similar problems when inserting
** refactor and clean up
This commit adds a script nammed 'listmailuser'. './setup.sh' uses this
this script for its subcommand './setup.sh email list'. A test have
been added too.