README.md: Missed a semicolon in the dump files nginx example.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
walkthrough.md: Added the dump sharing lines to example nginx configuration, commented out.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
Arthur: Add (optional) link to dumps next to fluxbb link in Arthur.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
Arthur: Fixed dump link.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
(cherry picked from commit f2f49315e65bf3effefd182c7548165f439bb49a)