Have different displays for lightweight and annotated tags

It's been requested to show annotated tags' descriptions in the Commit pane, but that was considered too verbose. How about just indicating that a specific tag is annotated? (The two often behave differently, e.g. with `git describe`, so it's important to know.)

Some (perhaps ugly) suggestions:

• On the Graph, add an icon at the right edge of an annotated tag
• On the Commit pane, add an icon or "(annotated)" to the right of each annotated tag, or perhaps the first few words of the annotation