- (experimental) provide generic way to read magnitude values
- expose /api/metrics with values formatted specifically for prometheus, with relay and sensor data
- small tweaks to sensor init
Example config:
```
scrape_configs:
- job_name: 'espurna'
metrics_path: '/api/metrics'
params:
apikey: ['apikeyapikey']
static_configs:
- targets: ['espurna-blabla.lan:80']
```
Where ESPurna side has
```
apiKey => "apikeyapikey"
apiEnabled => "1"
```