Allow negative Usage/CounterToday

[jantenhove]

My current electricity usage/countertoday can be nagative because i have solar panels. Domoboard displays 0 whereas Domoticz shows a negative value.

[squandor]

hi @jantenhove could you send an screenshot of you're value/config, because in my config i used an virtual usage device with an negative value and it displays in the top tiles just like it supposed to do.