content type for /response

headers for content-type and content length for retrieving the response
from the target host. The content type is application/json utf-8
Fix bug in Persistence & HHTPCallBack test
Fix bug in Persistence & HTTPCallBack test
Merge branch 'Unstable' of https://github.com/telefonicaid/Rush into Unstable
Merge pull request #64 from telefonicaid/Issue#63

Issue#63, binary friendly behaviour
The correct servers are now stopped in Persistence-HTTPCallBack test
add encoding field only when the persistence includes BODY