Refactored SecondaryReceiverSettings

* Exteracted settings keys
* Replaced overloaded ctor with factory methods
* Fixed existing boundary check for max concurrency
* Added boundary check for max concurrency in public config method
Making sure that callbacks still works if callbacks receiver is turned off
Audit messages now ignores the callback override
Remove unit test

Its covered by the acceptance tests
Merge branch 'hotfix-2.0.1'