Handle Specific Occurrences of Variables

### Story ###
- https://www.pivotaltracker.com/story/show/78059226

### Notes ###
- update data_criteria variable accessibility for 1.9.3 tests
- add <code>handle_specific_occurrence</code> to handle specific occurrences of variables
- update document <code>register_source_data_criteria</code> to remove specific occurrence info
- added specific occurrence variable test