CSS: Implemented ValidateHsl() with more tests.

- A more robust solution for ValidateHsl.
- HSL specs: [//w3.org/wiki/CSS3/Color/HSL](http://w3.org/wiki/CSS3/Color/HSL)
- HSLA specs: [//w3.org/wiki/CSS3/Color/HSLA](http://w3.org/wiki/CSS3/Color/HSLA)