BUG #14835: Pick better range for log coloring.

When switching to using log colors, ParaView now picks a range based on
the current range, rather than picking an arbitrary range. The logic
used is:

If (data is all positive)
    Leave algorithm as is.
else (i.e., we have 0 or negative data)
    Possible-Min = max/(1e-4)
    If (Possible-Min < 1)
       Minimum = Possible-Min
    Else
       Minimum = 1

Change-Id: I21eabc08425a2b0fba6129991a1daacd63b9c431
Merge topic '14835_fix_log_scale_for_coloring' into next

da670c90 BUG #14835: Pick better range for log coloring.