TODO:
 - Closing all docked widgets causes an exception
 - Test out minimum dock container size and maybe increase it a bit
 - (Unrelated) Can't click and drag a scroll handle

Polish TOOD:
 - Change cursor icon when window is dragged
 - Prevent docking if available size is less than 20 pixels, otherwise there might be some weirdness

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Other things to remember:
 - Possibly add a way to have hidden widgets in the EditorWidgetContainer (like side-bars that pop on mouse over in Visual Studio)
 - A way to persist window states
 - Also a way to reset all widgets to original locations