Add support for vtkTable to vtkExtractSelectedThresholds.

vtkExtractSelectedThresholds didn't handle vtkTable. Fixed that.

Change-Id: Icf7092cb56b1c47d0f15d8c28924e57129a6f21f
Merge topic 'fix_extract_thresholds_for_table' into master

1c9adc2e Add support for vtkTable to vtkExtractSelectedThresholds.