jtebert/kilosim: Kilosim 0.4

This update to Kilosim involves breaking changes in the way that you compile and run your code. This release updates the build system to use CMake, which should make it easier to compile and use with different operating systems. For instructions on how to use the new CMake system, see the README. This release does not change the underlying behavior of the simulator when executed. To use this new release with existing code, minor changes may be necessary to your code for CMake to find all of your files. For an example of the code structure and a CMake file for compiling code that uses Kilosim, see the Kilosim Demo repository