Add scaffold for each class of core CI status

lib/gitlab/ci/status/core/canceled.rb

+module Gitlab::Ci
+  module Status
+    module Core
+      class Canceled
+      end
+    end
+  end
+end

lib/gitlab/ci/status/core/created.rb

+module Gitlab::Ci
+  module Status
+    module Core
+      class Created
+      end
+    end
+  end
+end

lib/gitlab/ci/status/core/failed.rb

+module Gitlab::Ci
+  module Status
+    module Core
+      class Failed
+      end
+    end
+  end
+end

lib/gitlab/ci/status/core/pending.rb

+module Gitlab::Ci
+  module Status
+    module Core
+      class Pending
+      end
+    end
+  end
+end

lib/gitlab/ci/status/core/running.rb

+module Gitlab::Ci
+  module Status
+    module Core
+      class Running
+      end
+    end
+  end
+end

lib/gitlab/ci/status/core/skipped.rb

+module Gitlab::Ci
+  module Status
+    module Core
+      class Skipped
+      end
+    end
+  end
+end

lib/gitlab/ci/status/core/success.rb

+module Gitlab::Ci
+  module Status
+    module Core
+      class Success
+      end
+    end
+  end
+end