Implement MoveBufferArea in Unix to enable using more cross platform support

[goblinfactory]

Implement MoveBufferArea in Unix to enable using more cross platform support.

Currently .NET console (of all things) is not properly implemented in .NET Standard 2.1.

If you look here : https://github.com/dotnet/corefx/blob/master/src/System.Console/src/System/ConsolePal.Unix.cs and search for PlatformNotSupportedException you'll see there are 17 console methods and props that throw this exception. i.e. are simply not support. The most critical of these that we need is MoveBufferArea which is required in order to provide scrolling support needed in all the windowing functionality.

        public static void MoveBufferArea(int sourceLeft, int sourceTop, int sourceWidth, int sourceHeight, int targetLeft, int targetTop, char sourceChar, ConsoleColor sourceForeColor, ConsoleColor sourceBackColor)
        {
            throw new PlatformNotSupportedException();
        }