allow half-stars in aggregate ratings (bug 971205)

This involved rewriting the SVG and applying it as a clipping path to a span (and a span:after) on the page using CSS. One span is the grey background, the other span is the blue background, both are overlaid on each other with the same clip path and depending on the number of stars to be show, the length of the blue one is changed.

Tested in both regular and small sizes (small only shows on mobile) in various views. The number of stars gets cached locally, so half-stars may not show up until the app is rated again.
Closer would be toFixed(1), but it still doesn't return the same values. Currently it returns integer-printing values, but toFixed would always have a ".0" for whole integers. I could change the CSS patterns to make it work, of course. A bigger problem is that, as verbose as what I've got it, it seems reasonably obvious to me what it does, while glancing at the one-liner feels less obvious to me what it is doing. I'm not attached though, can replace it if you like.