Document review.pp parameters a bit.

This is sourced from IRC, they may be entirely wrong of course.

Change-Id: I715db1ee3311eb67bbd63c03f0b1129e60d2cc36
Make gerrit DB setup match actual practice.

sudo su - mysql is the actual mechanism used by -infra folk.

Change-Id: I209f0e9e2cb3f4dd7ad012f39b6e6551c05c5e0e
Merge "Document review.pp parameters a bit."
Merge "Make gerrit DB setup match actual practice."