Renamed lastModified to _lastModified_
Improve meta iteration methods

Remove _relations_, _forEachObject_, _iterate_ and provide _forEachRelation_, _forEachItem_ and _everyRelationDeep_ methods
Move forEachReverse tests to right module
Improve forEachReverse validation
Safer serialize logic
Tests for event imports
Fix rel:reverse validation
Fix rel#validateConstruction

It must use validateCreate instead of validate
-- lint
Customizable deep relations iterator