Fix undo/redo not working correctly with display properties.

Create an undo-set before applying changes for the display properties. Since
it's not cheap to determine the label for the property in pqPropertyWidget, we
don't use any for now.

Change-Id: Icd073192d2c4a7318aae6b869a7e259b8d1ead52
Merge topic '13450_update_tests_to_use_new_panels' into next

a7d1fae Fix undo/redo not working correctly with display properties.