Override prettyPrint's colour choice (red) for strings in quotes.

I've moved the docs.css to last so it can tweak any existing css, and
then set that to the same grey colour used for 'normal' text.

While testing I found and fixed an over-zealous line wrap.

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Merge pull request #7987 from SvenDowideit/stop-hurting-blackrosezys-eyes

Yep, its been hurting my eyes too - and you've finally inspired me to fi...