Update convert help text
Add Mercurial as a source format, clarify that the include directive triggers the exclusion of all not explicitely included files/dirs and use MAPFILE instead of revmapfile in the text, following the short message convention.
#header#
<title>#repo|escape#: changeset #node|short#</title>
</head>
<body>
<div class="buttons">
<a href="#url#log/#rev#{sessionvars%urlparameter}">changelog</a>
<a href="#url#shortlog/#rev#{sessionvars%urlparameter}">shortlog</a>
<a href="#url#tags{sessionvars%urlparameter}">tags</a>
<a href="#url#file/#node|short#{sessionvars%urlparameter}">manifest</a>
<a href="#url#raw-rev/#node|short#">raw</a>
#archives%archiveentry#
</div>
<h2>changeset: #desc|strip|escape|firstline#</h2>
<table id="changesetEntry">
<tr>
<th class="changeset">changeset #rev#:</th>
<td class="changeset"><a href="#url#rev/#node|short#{sessionvars%urlparameter}">#node|short#</a></td>
</tr>
#parent%changesetparent#
#child%changesetchild#
#changesettag#
<tr>
<th class="author">author:</th>
<td class="author">#author|obfuscate#</td>
</tr>
<tr>
<th class="date">date:</th>
<td class="date">#date|date# (#date|age# ago)</td></tr>
<tr>
<th class="files">files:</th>
<td class="files">#files#</td></tr>
<tr>
<th class="description">description:</th>
<td class="description">#desc|strip|escape|addbreaks#</td>
</tr>
</table>
<div id="changesetDiff">
#diff#
</div>
#footer#