Add experimental build support for Non-Windows Systems

[MattRCole]

• Update WaratahCmd.csproj to use ILRepack instead of ILMerge.

• Remove the use of Colorful.Console due to hard reliance on kernel32.dll

With Microsoft making an effort to be open-source, and mono's support of a large portion of the .Net Framework, it might be time to revisit #10 just in case the stance of the team/company had changed.

I've taken some guesses with the wording in the NON_WINDOWS_BUILD.md file that should be reviewed IE: building for non-Windows systems will not be officially supported.

[MattRCole]

@microsoft-github-policy-service agree

[matwilli]

While the effort gone to here is appreciated, attempting to maintain (what would be indefinite future) combability with other runtimes isn't something we can feasibly do. The .NET Framework is sufficiently stable and available to systems that we have committed long-term support for.