add support for SVG for star rating sprites
optimise svg file
Merge branch 'master' into star-ratings-svg

Conflicts:
	common/app/views/fragments/commonCssSetup.scala.html
Merge remote-tracking branch 'origin/master' into star-ratings-svg
Merge pull request #4605 from guardian/star-ratings-svg

add support for SVG for star rating sprites - Fixes #4176