Don't claim FreeBSD support
Manual: Bump date
Combine introduction / quick start parts
Update quick start section
Update installation section
Don't create unnecessary substitution goals for derivations
Build derivations in a more predictable order

Derivations are now built in order of derivation name, so a package
named "aardvark" is built before "baboon".

Fixes #399.
More build-cache-failures -> build-cache-failure