Introduction updates

* Add equivelent SQL to the first example
* Add link to Activator template in "What is Slick?"
* Change the features to match the home page
* Add code examples for the features
* Remove the quick overview since there is now a link to the Hello Slick template and we should rely on the Getting Started section to cover that content
manual SQL to plain SQL
Merge remote-tracking branch 'refs/remotes/origin/pr/580'

Conflicts:
	src/sphinx/introduction.rst