Add http and/or https to environment variable PIHOLE_HOSTS

[pluim003]

Clarification:

As I entered my pihole-host it wasn't found as automatically http:// was added to it, whereas I use https. Then thought of adding a variable USE_HTTPS (true or false) but with multiple pihole-instances this might also cause problems and would in my case as one is reachable from outside through https://pihole.somedomain.com whereas the other is internal with http;//:

[pluim003]

One of the modification later was to take care that your series in influxdb won't look like piholestats.https://pi_hole but simply piholestats.pi_hole which means it will add data to your 'old' existing series.