Preconfigure Mibew domain on firstboot

[JedMeister]

Currently the Mibew appliance only requires the admin password be set.

However, the "URL of your website" in the current (v17.0) version (in the 'Messenger settings' - https://www.example.com/operator/settings) is preset to 'https://mibew.org'. The chat feature (which is the core point of Mibew) doesn't work until you change that the to the current domain (or IP if just using an IP).

I think that we probably need to either redirect to the domain by default, or at least make it clear that if the domain isn't configured, then it won't work.