Make it possible to reset password from within Roundcube

This enables and appropriately configures roundcube's password plugin. In order to make this work I had to change permissions on dovecot configuration files, which makes me a little uneasy but I couldn't find how to make only the directories executable by recursing in the ansible documentation. I was able to test this in a local environment and it is working there. I'm no longer able to successfully execute `nosetests -v` (even on branches I know the tests were executing successfully on before) locally so I don't know that they pass though I don't think anything in them would be affected by these changes.