#Issue 70: Implement standard diagram editing keys

src/main/java/ui/ActionPerformer.java

src/main/java/ui/ArrowListener.java

src/main/java/ui/JMenuBarTurtle.java

src/main/java/ui/PanelKeyListener.java

src/main/java/ui/TDiagramPanel.java

src/main/java/ui/TGUIAction.java