Move the reception timestamping from the sinks to the REST handler
Fix the tests accordingly to the new timestamping mechanism
Modify the README accordingly to the timestamping changes
Add content-type and user-agent to the Constants class
Move the Http constants to the Http section in Constants
Merge pull request #71 from telefonicaid/enhancement/move-recv_timestamping

Move the reception timestamping from the sinks to the REST handler