Private setters

[REACH-113 Property setter for responses should be private](http://adsk-oss.myjetbrains.com/youtrack/issue/REACH-113)
@Benglin  yes, success status is default https://github.com/Benglin/Dynamo/pull/218/files#diff-554314b53506423ea6eed463abc1a301R18
I've done this way because if we send result data we assume no error