Changed background color of graph display to white. Looks much better,
IMHO.
added tooltipps, fought with Umlaute :->
increased tooltip dismissal delay to 10s, so we can read them
minor tooltip text edits, and re-enabled graph surface
now, re-enambled grpah for real
small edit to avoid compiler warning
some editing to make code more readable
on graph surface, made top/bottom AxisOffset smaller (=nicer)
corrected placement of label on lower "pH" axis.