Avoid assuming that AC inputs have unique types

[blammit]

Currently there is an assumption that AC-in 1 and AC-in 2 always have different types, i.e. they cannot both be grid, or both shore, or both generator. Discussed with Izak in #1626 that this is not a valid assumption:

"It is possible (though probably rare) for both inputs to be generators. It is also technically possible (though probably rare, and almost always a configuration mistake) to configure both inputs the same for any of the other types, so it is probably better if such an assumption isn't made."

Removing this assumption would require some reworking in AcInputs.qml to provide AC input measurements from the individual services, instead of just getting them from system /Ac/ActiveIn/.