ENH: added support for ScalarVolume inheritant

Before that it was impossible to choose ScalarVolume derived as IO node.
[There was a discoussion on thath](https://discourse.slicer.org/t/simple-filters-node-selector-doesnt-accept-scalar-volume-child-nodes/22571)

Author: kerim371

SimpleFilters/SimpleFilters.py

@@ -849,7 +849,7 @@ def create(self, json):
     self.outputSelector.renameEnabled = True
     self.outputSelector.noneEnabled = False
     self.outputSelector.showHidden = False
-    self.outputSelector.showChildNodeTypes = False
+    self.outputSelector.showChildNodeTypes = True
     self.outputSelector.baseName = json["name"]+" Output"
     self.outputSelector.setMRMLScene( slicer.mrmlScene )
     self.outputSelector.setToolTip( "Pick the output to the algorithm." )
@@ -890,7 +890,7 @@ def createInputWidget(self,n, noneEnabled=False):
       inputSelector.removeEnabled = False
       inputSelector.noneEnabled = noneEnabled
       inputSelector.showHidden = False
-      inputSelector.showChildNodeTypes = False
+      inputSelector.showChildNodeTypes = True
       inputSelector.setMRMLScene( slicer.mrmlScene )
       inputSelector.setToolTip( "Pick the input to the algorithm." )