Addressed a minor code review feedback
Fix MAGN-1045 (output port missing for array element modification)
Made use of "MapIdentifiers" to generate value for "previewVariable"
Refactored and simplified "GraphUtilities.Parse" method
Added new test case "Defect_MAGN_1045" to verify the fix
Merge pull request #1494 from Benglin/CodeBlockArrayPortFix

I'm merging this in to ```Master``` since it has been code reviewed before and was merged into ```ChocoButter2b1```.