Plot Template updates (#9002)

* Ensemble plot templates now have .erpt extension and new icon
* Default plot templates are given a checkmark overlay on the icon
* Context menu has been cleaned up a bit
* Old default template is really just the last used template. Rename it.
* Add max. recursive depth setting in preferences for plot template searches
* Only create plots based on correct template type when importing ensembles or single cases
* Support creating new plot from template explorer
* Update last used template when creating a new plot from a template

ApplicationLibCode/ProjectDataModel/PlotTemplates/RimPlotTemplateFileItem.h

@@ -36,6 +36,12 @@ public:
     void    setFilePath( const QString& filePath );
     QString absoluteFilePath() const;
 
+    bool isEnsembleTemplate() const;
+
+    bool isDefaultTemplate() const;
+
+    void updateIconState();
+
 private:
     caf::PdmField<QString> m_absoluteFileName;
 };