Fix typos and formatting in site docs and add faq entry about changing ports

Updated the site documents by fixing typos and adding some formatting where I thought it was appropiate.
Also added an FAQ entry: "How can I run Continuum on a different port?"

Note: I had some trouble generating the site using the released version of Maven 2. When issuing the command
mvn -U site
some pages looked weird, even in sections that I had not touched. The pages are the ones using the fml format, i.e. about.fml and faq.fml. The problem appears when using the "source" element more than once within the same "answer" element. This might be a bug in the site plugin for Maven 2. Please advise me if I should open an issue for this for maven-site-plugin.