Make links to fixtures from manufacturer absolute

[fxedel]

Links to fixtures from manufacturers (like in /cameo) aren't absolute, so they don't have a leading slash (e. g. cameo/thunder-wash-100-rgb instead of /cameo/thunder-wash-100-rgb).

This can be a problem if the url has a trailing slash (which should generate the same page) because relative links will then point to a non-existent subfolder. For example, in /cameo/, the first fixture's href is cameo/outdoor-par-tri-12 which results when clicking it in /cameo/cameo/outdoor-par-tri-12 which gives a 404 error.