Rewrite the SimHeat functions in Micropolis.Main.cs

[lloydsparkes]

https://github.com/lloydsparkes/MicropolisSharp/blob/master/Micropolis.Core/Micropolis.Main.cs

The code is pretty nasty, and uses "fake" mem copy and tries to mimick pointer maths from the original.

Rewrite it to become Idomatic in C#

[lloydsparkes]

The functions have been documented, and generally understood. Now they just need rewriting