BUG: adjust hidden flag on model hierarchy nodes to get back to previous behaviour

Libs/MRML/Core/vtkMRMLModelHierarchyNode.cxx - set hide from editors to false as a default
Modules/Loadable/Models/Resources/UI/qSlicerModelsModuleWidget.ui - set showHidden to false
Modules/Loadable/Models/qSlicerModelsModuleWidget.cxx - take out call to setShowHiddenForTypes
Libs/MRML/Widgets/qMRMLSceneHierarchyModel.cxx - set hidden true on new 1:1 hierarchy nodes
Modules/CLI/ModelMaker/ModelMaker.cxx - ditto
Base/QTCLI/qSlicerCLIModuleUIHelper.cxx - set show hidden to false and setting the node type by directly checking multiple and aggregate.

Issue #2906



git-svn-id: http://svn.slicer.org/Slicer4/trunk@21657 3bd1e089-480b-0410-8dfb-8563597acbee