misc features

This patch provided the following :

- corrected bug preventing correct checking of security parameter of the mailbox

* added email informing user that the submission has been processed.
* prevent mailhandler to send email to strangers (potential spammers).
* command matching now with preg_match, something like "truc: bidule" is now allowed.
* added Mandatory Commands : commands that will override those provided in the email.
* added optional AntiSpam code : this code is checked instead of the password. Thus providing protection from spammer/viruses without making password wandering on the Internet
* 'post by mail' permission is now per mailbox
* 'mailhandler settings' permission allow the user to change his settings

in order to this patch to work you will need to add an extra field to the mailhandler table, like this :

ALTER TABLE `mailhandler` ADD `mandatory_commands` TEXT AFTER `commands` ;

Note : this patch is related to 4.6 version of the module but include the javanaut and weitzman modifications.