Build: Fix Autoprefixer

Somehow got mixed up with the Sass target. Also had a errant semicolon
in the "last 2 version" browser setting
Merge pull request #3060 from nschonni/v4-fix-autoprefixer-options

Build: Fix Autoprefixer
Merge branch 'v4.0' of github.com:wet-boew/wet-boew into plugin-mediaplayer