(PDB-783) Release notes for PuppetDB 2.2.0

Signed-off-by: Ken Barber <ken@bob.sh>
I've added a blurb at the beginning. Structured facts is a word we use for both structured and typed facts, but I've broken it down at the beginning at least. If I could find a formative doc of Puppet's that spoke to this effect, I would link to it, but alas I can only find details.