added feed unit to tooltip and legend

[emrysr]

fix #26
added the feed unit to the chart legend and datapoint tooltip

also added the timestamp to the tooltip

[TrystanLea]

Thanks @emrysr

[pb66]

@emrysr & @TrystanLea,

Small point, but why is the unit being added to the feed name in the tooltip?

I don't see the need to have the unit in the tooltip twice and it just doesn't seem to belong with the feed name, it is specifically related to the value.

Likewise with the legend, the unit just doesn't belong there (IMO), unless somehow separated eg in brackets. If any where it should be on the axis scale not the legend.

Don't forget we have several keywords used in emoncms for the apps, this will lead to legends that read

emontx: solar_kwh kWh
emontx: export_kwh kWh
emontx: use_kwh kWh

it's just using up plot/tooltip area by extending the name string lenngth and not really adding anything useful.