Fix imperative ifnode ast comparison

1. Fix ast comparison
2. Add imperative ast comparison testcase
Merge pull request #3248 from junmendoza/defectfix

Fix imperative ifnode ast comparison
Merge branch 'master' of https://github.com/DynamoDS/Dynamo into Revit2015
Merge pull request #3250 from junmendoza/Revit2015

Cross merge to Revit2015