FAQ Redirects (closes #314)

[tkowark]

This PR introduces a means to gracefully redirect users when they are visiting non-existing anchors in the FAQs.
Example: Android app redirects to /faq/#39508. What happens now:

• App notices that anchor is not part of the FAQs
• Checks whether a redirect is defined
• If yes: scroll to anchor
• If no: Do a search using the provided anchor, which is hopefully an error code

Real life examples:

• #39508 refers to only one anchor (API39508) and, hence, a redirect is in place
• #9002 refers to a generic error. Hence, a search is performed