#24 Save editor state and restore

[MuteSoft Technologies]

When user closes the editor or the editor application shuts down abnormally, the last active state of editor (e.g. status bar, document selector, line numbers visibility etc.) should be saved and restored when editor is opened next time.

User's preferences can be overridden by last active state of editor.

Have an active editor state object and put important layout properties in this object. Serialize this object when editors state to be saved and sterilized when to restore editor's state.