key=23;0;0;0;0 and key=23;;;; lead to division by zero exceptions
This should fix this by ignoring empty strings for min/max (formerly
it got "converted" to float(0)) and also ignores min == max.
fixes#6828
The perfdata helper did an improper limitation as it might have skipped
valid values due to applying the limit before the filter. When not in compact
view the helper now also shows non-piechart values by using their raw
representation.
refs #6515
Prior to this change the PerfdataSet only knew the labels of a performance
data value which prevented the Perfdata object from being used
individually.
refs #6515
