OGLEdit files

OGLEdit comprises the following source files.

• doc.h, doc.cpp: MyDiagram, DiagramDocument, DiagramCommand, MyEvtHandler classes related to diagram functionality and documents.
• view.h, view.cpp: MyCanvas, DiagramView classes related to visualisation of the diagram.
• ogledit.h, ogledit.cpp: MyFrame, MyApp classes related to the overall application.
• palette.h, palette.cpp: EditorToolPalette implementing the shape palette.