Feat(feed2): determines if a revision is qualified for revert

[xinbenlv]

As per Feed2, we will only allow reverting when the revision is the last revision.

Feature request:

1. If the current revision is last revision of the page, show an icon of "LIVE"
2. If the current revision is the last revision of the page and the second last revision was not from the same author, allow reverting.
3. If the current revision is the last revision but the second last was from the same author, link to revisions for history.
4. If the current revision is not last revisions, show an icon to be "NOT LIVE"

4tmt