XD-2487 Reactor based MessageHandler for processors

XD-2487 : Create a Reactor based MessageHandler for processors

Updated with PR Review comments

* fix typos in various places
* change compile time dependency from dirt to spring-integration-core
* add timeout to receive calls in test
* remove unused service-activator in XML test config
XD-2487 Polishing

   Fix the tests to use distinct channels/messages
   Add service activator for pojo processor
   Fix compiler warnings