Move settings saving/resetting to pqProxyWidget

This was available in pqProxyWidgetDialog, but it is more widely
usable than just that GUI element, so it has moved to pqProxyWidget.

Change-Id: I3145a645b06228d8bc9f7b3840edd8bc124afa1c
Removed unimplemented method for setting vtkSMInputProperty setting

It wasn't needed.

Change-Id: I09545d01f2a0f7ed92fc2768b00586db0df49ec8
Added emission of missing signal

Added emission of changeFinished() signal to
pqProxyWidgets::onRestoreDefaults() to mimic the sequence of signals
emitted when settings are changed via the GUI.

Change-Id: I9693768ff4c5fe6fe39356b5d2cde4860e07243d
Removed unneeded includes and forward declarations

Change-Id: I9a522b5030d4bc69c37951db9f0677b0af1f815f
Changed some proxy property attributes

- disallow custom defaults for ViewSize in the ViewBase class

- added empty string defaults to various title properties so that
  their defaults can be saved and restored properly

Change-Id: I24733673c3fd987c52a21dae9197e819088bc7ee
Added buttons to save/restore defaults

Added buttons to save and restore default property values in the
properties, display, and view panels. Each panel has separate buttons
so that the settings for the proxy associated with each can be
saved/restored separately. This makes it possible to save settings for
a source without saving settings for the representation of that
source.

Change-Id: I53be2036de78905f59eb8524faa372bc4e38e65e
Fix tests.

Change-Id: I943461e8303b845c359cb72f2d1149d74103488b
gerrit: push data to gerrit when pushing topics to the stage

Change-Id: If9551ec985b6acbf187bb29bc77351549504cb8f
Merge topic '14790_save_restore_settings_buttons' into next

f2a2d69a Fix tests.
cd5fdd60 Added buttons to save/restore defaults
c1b2732a Changed some proxy property attributes
6619fcca Removed unneeded includes and forward declarations
067d857e Added emission of missing signal
82edead2 Removed unimplemented method for setting vtkSMInputProperty setting
6656aefb Move settings saving/resetting to pqProxyWidget
Merge topic 'stage-push-data' into next

d769625f gerrit: push data to gerrit when pushing topics to the stage