DUI: tests for conveters.

Last PR, but not least ;)
This is related to a [previous pull request](https://github.com/Benglin/Dynamo/pull/154).

![image](https://cloud.githubusercontent.com/assets/8158404/5047006/688bfcbc-6c19-11e4-86f6-e1ffb8389e39.png)

Reviewers
@Benglin ,@vmoyseenko, please take a look.

Link to YouTrack:
[MAGN-5282](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-5282) DUI: Add unit tests for all Sitrus converters