Merge branch 'stable-3.4'

* stable-3.4:
  Send/receive Event object instead of EventMessage
  Use EventGsonProvider binding from Gerrit core
  Use event deserialization logic from events broker
  Implement async send method as per 3.4.0-rc2 API
  Deserialize Event and EventMessage
  Use EventGsonProvider from Gerrit core
  Fix properties in EventConsumerIT tests

Change-Id: Ia534d42980f0949b3954e0eca23b8a74cc3be3ea