Add Instructions for running the software on macOS and Linux and configuring a development environment on these platforms

[retroric]

The original ReadMe.md has instructions for running the software and configuring a development environment on Windows platforms.

It would be nice to add instructions to run the software in macOS and Linux with Mono, and how to set up a development environment based on MonoDevelop.

Ideally these new instructions should be added to the original ReadMe.md file.