Fix for showstopper defect MAGN-261

#### Background
This pull request is meant to resolve a crash in Dynamo:

MAGN-261 Paste input/output node is crashing Dynamo
http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-261

1. Fix: MAGN-261 Paste input/output node is crashing Dynamo
2. Added three new test cases to verify the fix
3. Added "InternalsVisibleTo" attribute to "DynamoCore" so its internals are visible to "DynamoCoreTests.dll"

#### Unit Testing
These new test cases are added to verify the fix:
* TestRecordModelsForModificationWithEmptyInput
* TestRecordCreatedModelsWithEmptyInput
* TestRecordAndDeleteModelsWithEmptyInput