DUI: NoMatchFound Button added.

So, it's done. I removed commented code, added `NoMatchesFoundButton` to `LibrarySearchView` and created appropriate event, when user press on it.
This event clears `SearchText` in ViewModel, as result search textbox clears as well.
:innocent:
Reviewers
@Benglin,@vmoyseenko, please take a look.

Tasks on YouTrack:
[MAGN-4806](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4806) DUI: Present "No matches found" label if nothing is found
Are we seeing this as ```null```? If so, when will that happen? Document it here will be helpful (because I don't think there will be a case it will be ```null```, maybe you're just being very careful).