Make features profile changes trigger re-review (bug 862449)

https://bugzilla.mozilla.org/show_bug.cgi?id=862449

Note: this PR depends on #810, because I didn't want feature profile changes caused by reviewers to trigger re-reviews. Since #810 is not merged yet, there is an extra commit you shouldn't consider when reviewing, I'll rebase everything when this is done. At the moment, the only relevant commit for this pull request is 0fcd3db.

(Alternatively wait till we merge #810 before reviewing this)