Feature/iotcore 110 restrict proxy function scope

Address the following issues:

https://github.com/telefonicaid/fiware-orion-pep/issues/7
https://github.com/telefonicaid/fiware-orion-pep/issues/6
https://github.com/telefonicaid/fiware-orion-pep/issues/3


Discused at skype. NTC