round_digits/max

[jschlyter]

Refactoring the sensors I have some questions on round_digits and max handling:

• round_digits should be handled by suggested_display_precision IMHO. For values that are calculated by the integration, we can round after calculation.
• max is something I never seen in other integrations. Has there been issues with overflow values from the API? Most integrations tends to just report what is given to them.

[jschlyter]

Perhaps @leeyuentuen can help?

[jschlyter]

Will be removed in #258 and #259