Entries on the review request page (reviews, changes, and the initial

status updates) now share the same base templates, with information

provided by the entry classes on the Python side.
The base template provides the general structure used for boxes on the

review request page, handling anchors, avatars, labels, the header,

banners, and container for the main content. The specific entries

subclass this, filling out the necessary blocks to set the CSS classes,

header title, entry content, labels, etc. that are needed.
Avatars are based on a new avatar_user attribute on entries. If set,

and if avatars are enabled, that user's avatar will be rendered.

Templates can also provide custom images to use here.
There's now only a single JavaScript template for constructing the

model/view for each entry. The data and options are provided by new

methods on the entry classes on the Python side, as are the names of the

model/view JavaScript classes to use.
These changes make it easier to maintain entries, and will lead to

extension-provided entries for the review request page.

Tested that reviews, replies, changes (with and without status updates),

and the initial status updates entries all looked correct and all had

complete functionality (replying, collapsing, revoking Ship Its, etc. all

worked).
Tested with avatars enabled and disabled.