[WO-188][WO-421] introduce password-based login

* add custom login ability
* encrypt email password
* allow arbitrary tcp connections
* add db migration script v3 -> v4
* add bug reporting capability with the axe logger
* fix nonexistent folder handling
* enable message upload after sent
* use plain text alternative body when replying to html mails
* Move set-credentials.* -> login-set-credentials.*
* Use login styles for set-credentials
* Make OAuth optional
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