hgweb: show changeset age in more places (gitweb and monoblue) mercurial.js has a process_dates() function that calculates relative age for a given date, it works for all elements with "age" css class. If those elements also have "date" css class, the original text is preserved and age is added at the end. This patch adds these two css classes in some pages in gitweb and monoblue that weren't already using this feature.

obsolete: drop usage of changectx in '_computecontentdivergentset' Changectx are expensive and not needed there. The use of `repo.set` denote old code that predate the introduction of `repo.revs` that we now use. On my mercurial repository 495 draft: before: 0.054239 second after: 0.046935 second On a mercurial repository with 115973 draft: before: 0.564548 second after: 0.130534 second