am 1af05493: refactored CssSchema to distinguish between a schema, a...

am 1af05493: refactored CssSchema to distinguish between a schema, a collection of property filters, and the properties themselves which are now instances of an inner class.  Added code to the policy builder to allow a styling policy to be created with a custom schema

* commit '1af05493':
  refactored CssSchema to distinguish between a schema, a collection of property filters, and the properties themselves which are now instances of an inner class.  Added code to the policy builder to allow a styling policy to be created with a custom schema.