Using language server protocal requires project.json file present in project #434
Description
When connecting a Java client to the omnisharp-node-client Language Server implementation no output is received without a project.json file present.
The requirements for .NET Core have changed with v2.0.0 replacing project.json files with the MSBuild/csproj format (https://docs.microsoft.com/en-us/dotnet/core/tools/project-json-to-csproj).
In regards to Issue #265, personally it was not whether the project was restored (As I restored the project with a .csproj file and had no output), but if a project.json file was present that enabled completion on my file.