Simplifying common parser tests
Implements margin shorthand parsing

Per specs on http://www.w3.org/TR/CSS21/box.html#propdef-margin and
http://www.w3.org/TR/CSS/
Implements Padding parsing

This is a straight copy/paste from margin.

Implemented per http://www.w3.org/TR/CSS21/box.html#propdef-padding and
http://www.w3.org/TR/CSS/