Add "kpm wrap" command

- Add CsprojDumper, a tool used to dump csproj references
- "kpm wrap" creates project.json wrappers for csprojs in 'wrap' folder
- "kpm wrap" updates global.json to include 'wrap' folder as sources

parent #827 
Extracted this method to a shared util class because I thought `kpm wrap` might need it. Turns out `kpm wrap` doesn't need to call this method. But I think sharing this method across projects is still a good thing, so I keep it here.