ui: Added option to show file directory in code view title (issue #556)

* relative to project file if shorter
* checkbox in preferences
* not enabled by default

src/lib/app/Application.h

@@ -48,7 +48,8 @@ public:
 
 	~Application();
 
-	const std::shared_ptr<Project> getCurrentProject();
+	const std::shared_ptr<Project> getCurrentProject() const;
+	FilePath getCurrentProjectPath() const;
 	bool isProjectLoaded() const;
 
 	bool hasGUI();