Improved documentation:

- A chapter on Slick Extensions
- More lifted embedding features: Deleting, Inserting, Updating,
  Query Templates, User-Defined Functions and Types
- Structured list of supported primitive types
- Correct slick artifact spec in gettingstarted.rst
- Better auto-generated names for inner classes in apilinks.py
- Link to ScalaQuery for Scala 2.9 in introduction.rst (fixes issue #68)