Bug 1082853: Configure CSSLint and validate MDN CSS

Made a more decerning vendorize mixin with lookup tables for values.
Made a mixin for creating rgba fallbacks.
Remove table.activity which was presumably added back in during a merge somewhere).
Validate CSS, mostly working with outlines.
Merge pull request #2840 from stephaniehobson/BUG-1082853-csslint

Bug 1082853: Configure CSSLint and validate MDN CSS