Add '--in-place' option for "kpm wrap"

parent #964 

Functional tests for `kpm wrap --in-place` will be added after #956 is merged.
If there is an existing `project.json` for target wrapper project (i.e. `LocateExistingProject` returns a non-empty path), we don't need to create one under wrap folder, then there is no need to add `wrap` folder to global.json