Send api.fault notification on API service faults.
Send api.fault notification on API service faults.

Exceptions caught by the API middleware will now send "api.fault"
notifications indicating the offending URL and the underlying exception.
The allows the billing/usage systems to track requests end-to-end without
having to monitor log files. Disabled by default.
Enable with --notify_api_faults

Change-Id: Ied2783259413ba12d686b44b33e0707645e51afb

n0ano/gantt,n0ano/gantt