DUI: remove focus when mouse is over other member

This PR should be merged after [that](https://github.com/Benglin/Dynamo/pull/166) one.
Should be selected only one member. Mouse has more priority.
![image](https://cloud.githubusercontent.com/assets/8158404/4885108/e4b5989e-6371-11e4-93ae-858c91339514.png)


Reviewers
@Benglin ,@vmoyseenko, please take a look.
Link to YouTrack:
[MAGN-5266](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-5266) DUI: Remove keyboard selection when member is hovered by mouse