GitLab

* #1456 - Add "new sketch" in gRPC .proto, regenerate .pg.go. Use "user" dir for sketches created via gRPC

* #1456 - Avoid using hardcoded extension (address comment).

* #1456 - Add optional dir field in the request, use it.

* #1456 - Use go-paths-helper

* Use gRPC function from CLI to create new sketch
Co-authored-by: Silvano Cerza <silvanocerza@gmail.com>