Add a simple Gerrit review wrapper

This only allows the setting of reviews, and then only the message
and verification state, but should cover all that we need here.

Change-Id: I06d2decaf0a42e879b317b0cc054ac39315f0df8
Add an SSH based Gerrit review wrapper

This implements the same interface as the HTTP one in my previous
commit, but since we're already talking to Gerrit over SSH potentially
avoids having to configure to different mechanisms.

Change-Id: I374320553b565932ca54404a07dfe566d24df728
Add our LDAP connection

This is a wrapper around the existing srusers repo.

Change-Id: I6fde8c79dd56e110e965f4543654d885eaab3327