Review Board 3.0 introduced standardized anchors for comments and handy

icons for getting the link to the comment when hovering over, helping

reviewers point to specific comments without digging through the HTML.
These were only provided when loading a page, though. When publishing a

draft reply, those anchors and hover links wouldn't be made available.

Although reloading the page would make them appear, it was an annoying

oversight.
This change adds in the HTML for these when publishing a reply. To keep

the JavaScript side's logic fairly minimal, we inject the namespaced

prefixes specific to certain types of replies (diff comments, header

replies, etc.) for the anchor in the HTML as a new data attribute, and

fetch that out on the client side. This lets us keep all our logic for

differentiating anchors solely in the server-side templates and template

tags, so that we won't have to further rework the client-side code as we

introduce new types of replies.

JavaScript and Python unit tests passed.
Created replies for reviews headers and footers, diff comments, general

comments, and file attachment comments. Verified that the anchors worked

and that the links took me to the right spot. Also verified that they

matched the anchor names on page reload.