Migration and test cases

- Add a test case for [MAGN-3487](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-3487) by re-migrating the existing similar test case for [MAGN-2375](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-2375) back into 0.6.3 (following up the previous [pull request](https://github.com/DynamoDS/Dynamo/pull/1666#issuecomment-43580825))

- Migrate "XYZ Grid" into custom node

- [MAGN-3498](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-3498) We should not create Vector.AsPoint while migrating XYZ Dot Product node.