wip: big refactoring

Moving files.
wip: Big refacto

The admin application is now a true extension.
wip: Big refacto

Top menu is back.
wip: Big refactoring.
wip: Big refactoring

Limits extension OK.
wip: Big refactoring

autoreply extension OK.
wip: big refactoring

stats extension OK.
wip: big refactoring

Webmail still needs work.
wip: big refactoring

* sieve extension still needs work
* auth application removed
wip: big refactoring

Webmail template tags.
wip: big refactoring

amavis extension still needs work.
wip: big refactoring

old userprefs application removed.
wip: big refactoring
Useless import removed.
If a limit is specified, we have to make sure the value is a string before trying to limit it, otherwise the code fails if the value is not a string (e.g. an integer).
jquery.sortable.js is now needed by quarantine.js
Added everything needed to get the spam score out of the database and be able to sort on it (or any other data presented to the user).
Added support for sorting the table that is shown to the user.
Specify a default order in the default URL.
Perform the sorting at the SQL level instead of Python.