Update flot to 0.8.2.

Flot 0.8.1 had some bugs with pie charts that were causing occasional
and hard-to-reproduce bugs with the diff complexity icons. This updates
to 0.8.2, which fixes those bugs and many others.
Improve the style and maintainability of the new Markdown links.

This polishes up the Markdown links for the various edit fields. They're
now blue and don't have an underline, and they're also much shorter.
Particularly for the comment dialog, where it was taking up valuable
space and making it harder to drag the window.

For the comment dialog, the text is now just "Markdown." For the other
fields, where we have room, it's "Markdown Reference."

This also cleans up the code a bit to put the links in the templates
instead of injecting them into the DOM elsewhere. For comment dialogs,
it's in the template now (and no longer displays when showing the
"you must log in" or "it's a draft!" messages). For the inlineEditors,
it's now MarkdownEditorView that sets it up and not each individual
instance.

The root of the user manual is now a main JavaScript constant instead of
repeated throughout the codebase, making it easier to maintain. Each of
these links reference it.

There's also some fixes for the links in the comment dialog, which
weren't pointing to valid addresses.
Move the diff complexity icon into its own view.

The logic for the diff complexity icon in the diff viewer is now its own
view, making it easier to reuse. It's also a bit smarter now, in that it
doesn't require a number of replaces or total lines to work (though
providing this information adds more detail to the icon).

With this comes a performance improvement. Previously, each icon was
calculating the necessary colors for itself, but now they're calculated
only the first time an icon is used, and cached for future icons.
Move attachment screenshot handling into new classes.

There are now four new classes for handling the rendering of
screenshots, file attachments, and their captions. These replace the
in-template and in-view logic that we previously had.

It also restores the ability to see the change entries for removed or
uploaded file attachments and screenshots, which went missing after
moving to the new field classes.

Unlike the new DiffField, none of these classes handle recording the
change entries. This is because publish() performs many operations on
screenshots/file attachments, and it would just end up being more
complicated and less efficient to move that code out.
Show RRs from inactive users on "All Review Requests" and their user page.

Long ago we made a change that hid review requests from inactive users from the
dashboard. Unfortunately, this went way too far, hiding them from all
datagrids, including "All Review Requests" and their user page. As funny as it
is to "disappear" someone when they leave the company, it does make it harder
for people who are trying to find old changes.

Testing done:
* Set a user who had a couple old review requests as inactive. Saw that I could
  now see their changes in /r/ and /users/<user>/. Verified that their pending
  changes were still hidden from my dashboard.
* Ran unit tests.

Fixes bug 1436.

Reviewed at https://reviews.reviewboard.org/r/5488/