Unit test added.

see #394
Ensure that a recipient is unique inside a distrib. list.

fix #404
Don't allow mailbox quota values greater than the domain's one.

fix #401
Set 'admins' as the default tab when needed.

fix #405
Quota support improvements.

* A mailbox can now use the domain's default quota. (fixes #402)
* Possibility to define unlimited quotas (fixes #343)
Associated migration scripts. (see #343 & #402)
Oups :p

see #394
Remove the mailbox from the filesystem before the db record.

see #389
Simple user: Rename the mailbox when the username is modified.

fixes #407
Better handling of international string in sent emails.

fixes #409
The from field should not be changed.

fixes #408
Fixing encoding issue.
Smarter decoding attempts...

see #410
I think it is the best solution I've found until now...

see #410
Shortcut to list the identities of a specific domain.

fixes #337
Quotas page improvements:

* Possibility to filter mailboxes using a search pattern
* Possibility to edit a mailbox

fixes #391
Show table headers on the quarantine listing page.

see #223
Don't display column's name by default if not label is defined.

fixes #223
Few fixes:

* Take care of special characters (fixes #406)
* Don't try to select a non existing object (fixes #411)
Refactoring and Shorcuts added:

* Possibility to create an administrator with a new domain
* Possibility to create default aliases with a new domain

fixes #344