Add priority method to text preprocessor, improve handling of negatives.

Implement counter-styles into counters infrastructure.

Parse list-style longhand properties, tweak counter-lookup.

Test & fix rendering of Ethiopian 1.

Simplify counterstyle API & implementation.

Test & fix rendering ethiopian numbers.

Draft Ethiopic numbering implementation.

Add support for chinese, with correction regarding handling negatives.

Minor corrections to counter rendering.

Unit tests & bug fixes for counter-renderers.

Draft @counter-style support, with sample CSS.