In Havana, switch back to a driver-based wikinotifier.

Havana has switched away from the monolithic plugin framework
and now uses a coalition of entry points and drivers.  Messy, but
should still support everything we were doing before.

Change-Id: I6c3fe0caa6ede811cec1490c8e9edbd22a7f505f
Merge "In Havana, switch back to a driver-based wikinotifier." into production