Split API / Prometheus Endpoint / HTTP logic

[Azathoth-88]

Dear DnsCrypt Team,

I wonder if it would be feasable to to add an option to separately enable/disable the WebUI endpoint and only expose the json api.
I don't use the WebUI, i feed the json data to my InfluxDB instance, so it's sort of "redundant", not sure if other's using it in a similar fashion. This is obviously a very non-priority feature request. :)

Thank you for your hard work, much appriciated!