hgweb: rename 'changesetbaseline' template to 'difffrom'
More accurately reflects what it will be used for, and is also shorter.
This template is used to change which rev the current rev is diff'd
against. For example, if you're at '/rev/P1:REV', this would link to a
path like '/rev/P2:REV'.
Example usage in a template:
{parent%difffrom}
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-US">
<head>
<link rel="icon" href="{staticurl}hgicon.png" type="image/png" />
<meta name="robots" content="index, nofollow" />
<link rel="stylesheet" href="{staticurl}style-paper.css" type="text/css" />
<script type="text/javascript" src="{staticurl}mercurial.js"></script>