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
- Project references are added based on output assembly name
"kpm restore" only caches http responses with success status code
Expose the project build output folder to project.json
Fix test failure in ChangingLanguageVErsionIsEffective
Update the post build scripts to use project:BuildOutputDir