Adding support for visual group filtering to the browses view

For the `joomla.org` project, it would really help us to set up a Normal Releases view filtered on a single visual group to display large group of relevant categories (in this case, the translations for a single series (3 visual groups, one per series) and the main CMS downloads (a 4th group)) without displaying the full category tree.  This pull adds the Visual Group filter to the browses view's normal and bleeding edge layouts to assist with that.

There is one issue I'm still working to wrap my head around with this change and it deals with getting the right URL.  The incorrect menu alias is used when linking to the category.  As an example case, I have a Latest Releases menu item for the CMS downloads, a Normal Releases view (with this patch) for the Joomla! 3 Translations, and another Normal Releases view for all CMS downloads.  The Latest Releases view links to the category with the route `joomla-3-translations/joomla-3/joomla-3-3-3-6` but I'd expect the route to be `joomla-cms-downloads/joomla-3/joomla-3-3-3-6`.  I know Visual Groups came about as sort of workaround to another issue, but being able to pull this off would help us with the setup and front-end navigation massively.