Fix typo in kahadb troubleshooting doc and change title of FAQ

This patch fixes a title in the KahaDB docs, it also changes the title of the
FAQ to 'Frequently Asked Questions' to reflect its real purpose now that we
are attempting to create a more precise troubleshooting area.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #483 from kbarber/maint/master/mispelling

Fix typo in kahadb troubleshooting doc and change title of FAQ