Fix configuration error in Visual Studio

[PhilJollans]

On opening the RealTimeGraphX solution in Visual Studio I get the error message "Current solution contains incorrect configurations mappings. It may cause projects to not work correctly. Open the Configuration Manager to fix them. "

This - I believe - is because the project file RealTimeGraphX refers to a Debug configuration, but the tag <Configurations> only specifies the Release configuration.

Simply adding Debug to the <Configurations> tag fixes this problem.

Note: I'm a newbie when it comes to Pull requests. I checked in two other changes which I did not want to be part of the pull request, and then reverted them. That is why there are three commits in this pull request. The only relevant change is in RealTimeGraphX.csproj.