Add user warning on startup

notify the user of the use of dev software

ToDo: the text still needs to be adjusted

sources/qet.h

@@ -28,10 +28,19 @@ class QActionGroup;
 	anywhere else within the QElectroTech application.
 */
 namespace QET {
+	/// Read the release workflow documentation
+	/// before making changes here!!!
+
 	/// QElectroTech version (as string, used to mark projects and elements XML documents)
 	const QString version = "0.80";
 	/// QElectroTech displayed version
 	const QString displayedVersion = "0.80-DEV";
+	/**
+		@brief FileFormatStable
+		- On all non-release branches: false
+		- On release branches: true
+	*/
+	const bool FileFormatStable = false;
 	QString license();
 	
 		//Describe the current state of a graphic item