(docs) Update API Index to reflect all endpoints

We were missing quite a few endpoints from this index. I've also cleaned up the
ordering to match the LHS toc on docs.pl.com.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #1062 from kbarber/maint/master/update-api-index

(docs) Update API Index to reflect all endpoints
Change name of fact-nodes operator to fact-contents

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #1063 from kbarber/maint/master/rename-fact-nodes-endpoint

Change name of fact-nodes operator to fact-contents
(PDB-783) Release notes for PuppetDB 2.2.0

Signed-off-by: Ken Barber <ken@bob.sh>