* Add missing account registration for apps in postfix
* Also set email on dovecot DB
* fix undefined var
* Fix missing username format config in dovecot
tells dovecot to create standard folders on first login if they do not exist and which folder names are used for special purposes like archive, spam/junk, sent, etc.
For rspamd being able to learn ham or spam from messages being moved into spam/junk folders or out of them dovecot needs to know how spam/junk folders and trash folders are named.
The former rules narrowed the folders being recognized as spam/trash down to just 'Junk, SPAM, Trash' (case-senistive).
Since users and admins can change the foldernames and write their own seive filters to use those folders I think it is a big improvement if more folders will be recognized.
The change is supposed to accept some more commonly used folder names for spam and trash in a case-insensitive manner.
This is reasonably important for the performance of clients such as Delta Chat. The plugins are bundled with dovecot by default (see https://wiki2.dovecot.org/Plugins ) so this should not be disruptive.
