Save Ansible settings at the time of provisioning in the database.

Created by: smarnach

This makes sure the Ansible settings that are actually used for provisioning are stored in the database, instead of generating a settings string with the current values every time the settings are requested. This is more efficient and more consistent than the old version, and will hopefully resolve the issue with repeated requests to the Github API from the web process.

The data migration will fill in the current version of the Ansible settings for each existing instance. It's kind of a hack, but I don't think it's possible to do anything fundamentally better.