Ref T4266. This possibly moves us towards getting reasonable timeline grouping:
- Always sort icon stories to the top.
- Render one timestamp for the whole group, using the earliest tranaction date.
- Move any "Edit", "Edited", or "Preview" links to the top.
- Rendering just one timestamp implicitly fixes the JS issues.
- For stories without an icon, indent them if any member of the group has an icon.