Comment bundle 'label' == Node type name

Comments, as fieldable entities, have one bundle per node type.

The 'label' for those bundles, however, is exactly the same as the node type, which leads to a confusing 'Field list' (see screenshots).
This stayed hidden before #538164: Comment body as field and #537750: Field UI for comments.

Attached patch uses t('@node_type comment', array('@node_type' => $name)) as the label.