SmartMCB, Emylo smart meters: extract V, I, P from phase_a dp.
- Assume the same format as TOMPD meter, as the dp id is also the same.
- set phase_a to polled, as it does not seem to be reported by default.
- SmartMCB: remove deprecated switch (replaced with reset button)
Issue #110, #388, #529, #577