Removed redundant spaces.
Changed the signature of extractContent because it was not specific for HttpRequests.
Service-io-client got a bit of refactoring.

The functionality to extract the body of a http response was already made
in httpserver.dart. And every handle did the same thing with the response.
Made some refactoring in order to make it more human readable.
Made some changes to model.reception in order to comply with the managementserver.