add thunderbird autoconfigure files to webapp nodes
https://developer.mozilla.org/en-US/docs/Thunderbird/Autoconfiguration https://developer.mozilla.org/en-US/docs/Thunderbird/Autoconfiguration/FileFormat/HowTo
The file should be served from https://example.com/.well-known/autoconfig/mail/config-v1.1.xml
this way, the provider does not need to purchase a commercial cert for autoconfig.example.com.
The actual autoconfig file should returns entries that contain this:
bitmask.net Bitmask Bitmask localhost 143 plain password-cleartext %EMAILADDRESS% localhost 25 plain client-IP-address
(from redmine: created on 2013-07-19)