BUG #13811 - 3D widget visibility issues.

3DWidgets were staying visible even when the active panel was changed. Fixed
that. We were never calling select/deselect on the 3D widgets. Added logic to
pqProxyPropertiesPanel to ensure that we call those when the panel is
shown/hidden.

Change-Id: I1441518630a54674dbb2171c0d349f9a899b63b2
Merge topic '13811_fix_3Dwidgets' into next

bc7cf27 BUG #13811 - 3D widget visibility issues.