Refactored standard legacy panel to replace pqContourPanel.

This is part of the efforts to replace specialized panels with
pqStardardLegacyCustom panel. Now all specialized pqContourPanel features
have been migrated over to standard panels.

Change-Id: I83a8e8b2e2b34b1f2a1ebe0ebe2100fd03787f1c
Use GroupProperty for certain properties in filters.

To be consistent with the rest of the UI panels, the
ScalarValueListWidget and ProxySelectionWidget are integrated with the new
GroupProperty specified in the xml.

Change-Id: I7bcc817ef7e27e571e0e286838aae46f5afa364f
Added two UI decorator classes for properties depending on input type.

Two decorators are added for properties that should update enable state
based in input data types. One is for non-polydata type, the other one is
for structured data type.

Change-Id: Iaa9d765d361ea2c34afef608999fc3f4133bd0d3
Modified ExpanderButton style for Windows

Change-Id: Iaed69669ac1cb008312d522c619b9a946b3b8d28
Fix failing tests due to UI changes

Change-Id: Ieb8e0e0ca22dc308d55dc4609cc67219490d6946
Fixed unused variable warnings

Change-Id: I67b16aded45b3e97b66978fb62f426898b80f65e
Merge topic 'refactor_contour_panel'

cff472f Fixed unused variable warnings
598be95 Fix failing tests due to UI changes
5e7ebf0 Modified ExpanderButton style for Windows
fd432a5 Added two UI decorator classes for properties depending on input type.
ec9cdab Use GroupProperty for certain properties in filters.
1dad8e8 Refactored standard legacy panel to replace pqContourPanel.