top10: 1.2.1 - (RED) Fixed de-/serialization, turned of caching in IT

* Fixed the type-mapping for the `JsonDeserializer`.
* Disabled the caching / out-buffering in Streams.
* Both changes are necessary, to see in `Top10ApplicationIT`, that
  messages are processed: _Compare the outcome of the test before and
  after this commit!_
* Nonetheless, the integration-test still fails, because the assertion
  is not true.