Improve bug tracker CSS, especially for comments.

Add auto-linking to bug report and comment parsing.

Properly handle "file not found" events for log files, rather than
just allowing an Application Error to be raised.

Fix small comment typing error.

Tighten up filtering of Textile and HTML markup in forum posts, given
that spammers now sometimes get in and make posts. Use the mechanism
therein to fix Ticket #354, albeit at some significant speed penalty;
this occurs only when new posts are created or old posts are edited
and isn't too large compared with the wider request activity, for
typical length posts.

Fix Ticket #352.

Fix divide by zero (facepalm).

Various forum patches to work better with page and per-page parameters
during replies and editing inside topics. Fixes Ticket #351.

DRY up Changeset #446.

Fix Ticket #353.

Eager loading of the User object associated with the most recent
post in a Forum ought to speed things up, but in this context it
was causing a significant performance issue seen in particular
when trying to fetch the top-level list of forums. Just getting
rid of the eager-load instruction fixes the performance issue.

Implement what turns out to be a very simple fix to long-standing
irritation described by Ticket #169.

More efficient equivalent of part of Changeset #442.

Implement per-page selection (25, 50, 100 items) for lists of posts
and posts within topics, as per Ticket #261. RSS feeds for posts within
topics have been increased from 25 to 50 items in passing as these are
quite lightweight to process.

Fix bug raised in Ticket #285.