Include creator_id in project info of API

lib/api/entities.rb

@@ -54,6 +54,7 @@ module API
       expose :name, :name_with_namespace
       expose :path, :path_with_namespace
       expose :issues_enabled, :merge_requests_enabled, :wiki_enabled, :snippets_enabled, :created_at, :last_activity_at
+      expose :creator_id
       expose :namespace
       expose :forked_from_project, using: Entities::ForkedFromProject, if: lambda{ | project, options | project.forked? }
       expose :avatar_url