Extract EE specific files/lines for some service objects

We have the following files containing EE specific code. We should move them to ee/

• app/services/projects/destroy_service.rb => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19111
• app/services/projects/update_service.rb => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19117 / https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/5825
• app/services/boards/issues/create_service.rb => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19093 / https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/5810
• app/services/lfs/unlock_file_service.rb => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19017
• app/services/milestones/base_service.rb => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19018