Update to the docs outlined in #1887.
In particular, the changes do:
1. Require no property, have a working default for everything
2. Be clear about what gets printed and how.
Tests ahve been adapted to still pass.
Base the rewrite on testsuite/css/parser/test-css-parser - we now
require the node file to match a reference node and track the errors it
triggers.
We also no longer use gtester.
This adds a test tool gsk/node-parser that takes node files and parses
them.
A few of these node files have been added, for crashes I encountered while
developing the new parsing code.
