Add enhanced logging option

[n1nj4888]

Hi @frdmn,

I created this PR for enhanced logging as per my feature request (Issue #13) to add the option (SPEEDTEST_ENHANCED_LOGGING) to output all the speedtest-cli metrics to a single influx measurement (INFLUX_MEASUREMENT).

If SPEEDTEST_ENHANCED_LOGGING is not set, the code should work as it does currently writing the download, upload and ping metrics only to InfluxDB. If SPEEDTEST_ENHANCED_LOGGING is set then the code should work in the new way and log all speedtest-cli results to a single measurement (INFLUX_MEASUREMENT) - Obviously if SPEEDTEST_ENHANCED_LOGGING is set, the grafana dashboard will have to be amended. I haven't got around to doing this yet but have my own dashboard and it seems to work well...

This is my first PR and I'm not a developer by profession so there will likely be a better way to do some of this?

Thanks!

[jeanfrancoislarente]

@n1nj4888 - you should provide a default dashboard with the enhanced metrics!
I would take it for a test drive and report my experience here!