Support csproj files for identifying .NET Core projects

[omajid]

(This is a heads up for something that will become an issue in the future)

OpenShift supports .NET Core images and relies on project.json files to identify a project as .NET. An upcoming version of .NET Core will switch from using project.json files to ${PROJECT_NAME}.csproj files: .NET Core Tooling. This change is being added to Visual Studio right now and will be added to .NET Core in a later release (possibly in a couple of months).

OpenShift will need to update the detection routines to pick up these csproj files to identify a .NET Core project in addition to project.json files.

[jerboaa]

@bparees A heads-up for you so you can plan accordingly.

[bparees]

@jim-minter maybe while you're doing the updates for jenkinsfile support, you can go ahead and add this to the .net detection logic.