Merge pull request #166 from telefonicaid/bug/151

Bug/151 (into release/iotplatform-v1)
Rollback regarding the double quotes when obtaining an attribute value
Use the timstamp Flume interceptor
Document the new timestamping method
Add the timestamp Flume interceptor to the configuration template
Fix issues raised during code review
Merge pull request #171 from telefonicaid/hardening/143

Hardening/143