Add Save/Modified display in modeline

src/main/java/app/model/Model.java

@@ -9,6 +9,7 @@ import javafx.scene.Scene;
  * by multiple pieces in the application, including the primary scene.
  */
 public class Model {
+  private static boolean fileIsSaved;
   private static String activeFilePath;
   private static String currentProjectPath;
   private static ProgrammingLanguage currentProgrammingLanguage;
@@ -30,6 +31,10 @@ public class Model {
     return scene;
   }
 
+  public static boolean getFileIsSaved() {
+    return fileIsSaved;
+  }
+
   public static void setLanguage(ProgrammingLanguage language) {
     Model.currentProgrammingLanguage = language;
   }
@@ -37,4 +42,9 @@ public class Model {
   public static void setScene(Scene scene) {
     Model.scene = scene;
   }
-}
+
+  public static void setFileIsSaved(boolean fileIsSaved) {
+    Model.fileIsSaved = fileIsSaved;
+  }
+
+}