Storing the content of config files in the pillar removes templating

[simonwgill]

Storing full text in the pillar means that the values being saved in the file can't be determined without some trickery at highstate time.

As far as I can see, all the dovecot config files are basically the same structure as a section of the pillar, so a single template should suffice to convert YAML lists into those files. That way anything happening during the pillar merge (environments, etc.) would be reflected in the final files.