Email notification override for monitoring.

If notification_email_address is defined, use that instead of PagerDuty
for the notification plan.
Collect load balancer facts in monitoring.yml.
Actually, here's a better approach: tagging.
Register two sets of entities, checks and alarms.
Quote the with_items items.
Refactor monitoring zones into vars.yml.
Add monitoring zone source IPs to the whitelist.
Prefix `pagerduty_servicekey` with prod or staging.
Use separate PD credentials for staging.
Okay, this is how I actually want to do this.
Updates from my Ansible PR.
Only remove SSL termination on an empty dict.
Use variables to toggle email/PagerDuty.
Register things by name to avoid repetition.
Accept a "state" for ssl_termination in rax_clb.
SDK, not SKD
Actually use different labels from with_items!
rax_clb mocks.
Merge pull request #741 from rackerlabs/monitor-staging

Set up monitoring alerts on the staging server.