The doc generator only picked up the event types related to instance
actions because the doc generator looked up the registered notification
classes only. Until now, only the instance related notifications were
imported in the doc generation environment so the other notification
classes were not registered.
This commit explicitly imports the modules that defines the notification
classes to make the doc complete.
Change-Id: I269e05ddb62ec6c6cc7f7922c1344186ccf850d1
Closes-bug: #1640818