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
I don't know... Just remember last time, when I didn't check by null and you said,that I have to do it always)))