Multi Stage Docker Files

Multi stage Docker files allow you to have multiple from commands. This means that every time I do a Docker build, it's not having to process every single command each time. To take advantage of this cache, I would copy the CS branch files first. Then I would do a run.net restore. So that command is cached. And then I would Copy the rest of the source code in before I do my dotnet build. It won't invalidate that dot net restore layer and do a full dot net restore each time I do docker build.