Reuse 'edit' window

[objectDisorientedProgrammer]

Editing an existing entry and viewing are almost the same operation. Modify EditWindow.java to be used as both a view and edit window.

[objectDisorientedProgrammer]

• change 'edit' button in mainwindow to be 'view'.
• change textfields in editWindow to be isEditable == false by default.
• add button 'edit' within the editWindow that enables editing the textfields.