AllPlotWindow - Alt/Slope - improve texts

... improve texts for Imperial unit setting
Google Map Overlay

.. and interval hover on marker

.. need to also show interval on hover as gray path
   but find a way of doing it without duping the code
   in the webpage js.
AllPlot: show balance in stack view only if checked
AllPlot: in Stacked View = yes / By Series = no - Curves missing

... NP, AP, XP and TE, PS curve are not shown as indicated by "Checked"

when changing between rides, "Checked" settings are ignored