create vagrant testenvironment

[trees] - created external reachable mailserver

• creates testsetup with mariadb,postfix,dovecot,trees
• mailserver accessable via ssl
• domain: trees.testing
• SSL cert needs to be accepted when used with thunderbird
• only works with pwhash_algo 0 yet
• for further information see vagrant/README.md

(Mailserver is now reachable from outside the VM)

Closes #21 (closed)