User Permissons and some automations

[balli1187]

I changed the code in a way that user permissions are pulled into the container and also add some lines for automation:

• cronjobs are setup automatically. schedule can be defined by environment variable
• timezone can be setup by variable. Might be not necessary but should prevent changes in e-mails timestamps
• subdirectories (Maildir, sieve) arecreated if it doesn't already exist.

Hope you like it and can approve it.