Add button entity to reset Meter CC

[raman325]

From #17, it would be nice to provide users with button entities to reset the Meter CC instead of a service

If a device reports support for resetting meters, the end user must be able to perform this action. The driver exposes a writeonly value in this case, see node diagnostics.

For now, the user can reset a meter using a service call, which is sufficient for passing certification.

In the long run, we should add additional button entities, similar to PING or the planned IDENTIFY (Indicator CC).