Factorize out cascade logic.

Add method to override CSS inheritance.

Parse HTML 'style' attributes.

Fix parser freezes, blocking issue for Rhapsode.

Fix incorrect handling of invalid syntaxes.

Ignore invalid selectors.

Aid attribute sorting, fix install of internal modules.

Test cascade logic.

Test/fix cascade logic for selector specificity.

Switch to new namespace for consistency with other modules like css-syntax.

Draft alternate API.