style: in preparation for bootstrap, replace kallithea title class with bootstrap compatible panel-heading

This is a subset of a bigger changeset. The subset was extracted by Mads Kiilerich, mostly by:

sed -i 's,<div class="title\>,<div class="panel-heading,g' `hg mani`
sed -i 's,\<div\.title\>,div.panel-heading,g' kallithea/public/css/style.css