Add new notifications types for volumes/snapshots

This change allows to collect and view notifications of different types -
volume/snapshot.(create | delete | update).(start | end) and
volume.(resize | attach | detach).(start | end).

Implements: blueprint add-new-notifications-types-for-volumes-and-snapshots
Change-Id: I592605bcea483d06f219a4d02d3a70a9fc0e27a3
Merge "Add new notifications types for volumes/snapshots"