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 
This looks really wrong. Why can't we use just the method `PathUtility.IsChildOfDirectory` on all nuget package paths?