Use different options for exporting GL2PS charts.

Change-Id: I1691bfb3637edb74b62ef0a9002b895a4b429ef6
BUG #14303: Restore threshold panel to use two sliders

Revert "BUG #14158: Update threshold panel to use double-ended slider."

This essentially reverts commit 8107ac4f34730f949b8db912247e06aef4ae862c.

Change-Id: I6f0a70340df67ce9320be2b3ce6b9e4b1f4067e1
BUG #14392: Fix selection modifiers for chart views.

Added ability to change selection modifier while in selection mode as mentioned
in the bug report for BUG #14392.

Change-Id: I24afaf591fd972995dc209e4b7d1f0ba5abf87e3
Fix issues with ExtractCTHParts filter.

This addresses several issues with vtkExtractCTHPart filter by doing a refactor
that cleaned up some of the logic and implementation. Also added backwards
compatibility fixes for XML state files since the filters API was changed to
remove inconsistencies.

Addresses BUG #14396.

Change-Id: I3e6b66338351d972aaf487cae6e6d521a5f04ff3
Fix test after changes to filter UI.

Change-Id: Id65590d403bf1d1553b871843be02dcc6eb689dd
Merge topic '14303-restore-double-range-widget'

2ea9c6e BUG #14303: Restore threshold panel to use two sliders
Merge topic '14382-gl2ps-chart-options'

9133ced Use different options for exporting GL2PS charts.
Merge topic '14392_fix_modifiers'

1404bdf BUG #14392: Fix selection modifiers for chart views.
Merge topic 'fix_extract_cth_filter'

7273cff Fix test after changes to filter UI.
1aa4398 Fix issues with ExtractCTHParts filter.