Base Editor window class and interfaces to make it easier to implement editor windows. The BaseWindow class provides virtual methods that split up layout and repaint phases into different calls:

• OnDataUpdate - Called during the layout phase. Use it to refresh and cache values to be used.
• OnFirstRepaint - Called on the very first repaint event after OnEnable
• OnUI - Called after OnDataUpdate, equivalent to OnGUI (always called whenever OnGUI would be called)