Ref #3077: use modificationId in eventLog related APIs

Linked to http://www.rudder-project.org/redmine/issues/3077 and http://www.rudder-project.org/redmine/issues/3002


https://github.com/Normation/cf-clerk/pull/2 or https://github.com/Normation/cf-clerk/pull/3 needs to be accepted too (prerequisite of http://www.rudder-project.org/redmine/issues/3102)