Add a "refresh" button on activity feeds

(with preparation for other activity fetchs: at the end, in the
middle...)
Add a "load more" button at the bottom off activity feeds
Add a "load more" button in the "middle" of the activity feeds if needed

It's used when a click on "refresh" (or a "load more" button as we
describe here) does not fetch all the available entries
Check score+identifier to remove entry from partial activity
Display "Load missing" in midlle of the activity feeds
Correct comment with no commit attached
Auto update "timeago" in activity feeds