hgweb: make infinite scroll handling more generic and extensible
Namely, this allows the next page pointer to be not only revision hash given
in page code, but also any value computed from the value for previous page.
{header}
<title>Mercurial repository not found</title>
</head>
<body>
<div class="page_header">
<a href="{logourl}" title="Mercurial" style="float: right;">Mercurial</a> Not found: {repo|escape}
</div>
<div class="page_body">
The specified repository "{repo|escape}" is unknown, sorry.
<br/>
<br/>
Please go back to the <a href="{url|urlescape}">main repository list page</a>.
</div>
{footer}