Add HTTPS and Basic auth

[roidelapluie]

I would like to add HTTPS and Basic auth here, but I have some questions that influx experts might help grasp

Would this exporter still work with https?
Should we disable udp when we enable https?
Do you have further concerns about influx compat if we add tls here?

[matthiasr]

InfluxDB supports TLS so there should be no problem there. As far as I can tell, when you enable it it becomes the only endpoint, so I think disabling UDP in that case makes sense. Maybe we should, for simplicity, disable it by default?

[matthiasr]

As of 2.0, InfluxDB also dropped the UDP support.

[matthiasr]

Also, 2.0 only supports token authentication. We can do that later (#80) but I think it would be good if we could support that in general.