Shrink the FAQ

The wiki FAQ entries have been transferred to the main website FAQ. Now the page needs to be improved.

• Add all subheads to the top of the FAQ for easier navigation.
• Delete entries that are outdated, no longer relevant, or not frequently asked on the help desk.
• Consolidate Tor Browser and Tor Browser 3 subsections.
• Move sha256sum verification to the signature verification section.
• Migrate information on setting up a relay to a dedicated page.
• Migrate Abuse questions to the Abuse faq and kill the subsection.
• Dedicated page for Alternate designs we don't do yet.
• Kill Compilation and installation subsection.
• Consolidate questions that duplicate answers.