[TIMOB-7101] MobileWeb: CSS rule manager

Setting styles on many DOM nodes can be a huge performance issue and cause multiple reflows. The browser is capable of optimizing the number of style changes per reflow by applying a CSS rule that contains several style settings. A CSS rule manager would create multiple rules and apply them based on common style changes. For example, if ever DOM node is set to a specific font and color, it is more efficient for a CSS rule manager to create a rule, then add the rule to each node. We may need to break up rules into categories (background, font, size, pointer events, transitions, etc). Since the style properties will vary, perhaps a hash of the properties and their values can be used to speed up creation and applying of rules.