allow half-stars in aggregate ratings (bug 971205)

respond to feedback

fix link to svg

holy shit what was I thinking?

moving rounding method

moved rounding aggregate ratings to the right place

move rounding code to a filter

unitless 0
Merge pull request #501 from dethe/allow_half_stars

allow half-stars in aggregate ratings (bug 971205)
rename flag images to match localization settings (bug 1024230)