ENH: Made displayed node type configurable in qMRMLNodeComboBox

Configuration is useful for cases when a more specific type name is preferred (e.g., instead of the generic "Create new SubjectHierarchy" option, a module can set up the widget to show "Create new Measurements").

Added methods:
Q_INVOKABLE void setNodeTypeLabel(const QString& label, const QString& nodeType);
Q_INVOKABLE QString nodeTypeLabel(const QString& nodeType)const;

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25011 3bd1e089-480b-0410-8dfb-8563597acbee