`ent show`: visually distinguish issues and comments from each other

`git log` does it well:

* The first line of each commit (that says `commit SHA`) is in a
  different color

* The commit message is indented, making it visually distinctive from
  the commit header which is not indented

* There's a blank line after each commit, before the next one starts

Something similar in `ent show` would be good.