CSSTidy Code

Extra documentation for CSSTidy testing suite.

- Add discard_invalid_selectors cfg and functionality; this fixes some of the duplicate combinator problems
- Minor comment formatting changes
- SETTINGS and FULLEXPECT support added to csst tests

Minor formatting changes:
- Compress extended if/else statement to indicate chaining
- Remove trailing ?>, it's not necessary in PHP!
- Add a custom harness for all unit tests

Make unit tests use SimpleTest, integrate in the framework. We have a custom reporter.