Reverted OpenWire changes and updated README. Also removed old Darwin V12 code.

[cbailiss]

• Changes in Jan 2023 that switched the NROD code to using OpenWire have been reverted.
• Removed the old Darwin V12 code completely (it had been removed from the Visual Studio solution but the project files were still in the repo).
• Updated README to reflect that this code doesn't work well with the current open data feeds and added a reference to the new openwire-client-dotnet repo.

I have created updated versions of the dotnet samples here:
https://github.com/cbailiss/openwire-client-dotnet
This repo can be moved into openraildata if you are happy (see the README in that repo for how the code compares with what is in this repo).