Moving search functionality to LibraryContainerView

### Purpose

Create LibraryContainerView. This View will include `Library` label, Search textbox and LibraryView or LibrarySearchView. So `Library` label, Search textbox is the same for both views: LibraryView and LibrarySearchView. 

`LibraryView` is used for regular view.

`LibrarySearchView` is used for Search.

Let's take a look on left sidebar with `LibraryView`.
![001](https://cloud.githubusercontent.com/assets/8158551/4007959/be982a3c-29ce-11e4-8759-2e9b2c15e578.PNG)

For case of `LibrarySearchView` we will have this view of left sidebar.
![002](https://cloud.githubusercontent.com/assets/8158551/4008003/ba5ca78a-29cf-11e4-9568-7adc222bd532.PNG)

### Modifications

`SearchView` is renamed to `LibraryContainerView`. `TreeView` of old design is commented. At the end of file added instance of `LibraryView` and `LibrarySearchView`. The last one is created in this PR.

The idea of this `LibraryContainerView` to have search and switch between `LibraryView` and `LibrarySearchView`.

Additionally here is done functionality connected with switching between two views: `LibraryView` and `LibrarySearchView`. To switch developer should change `libraryView.Visibility`. In XAML for `LibrarySearchView` added DataTrigger which controls it visibility depending on `libraryView.Visibility`.

### Additional references

The PR was created from this PR: https://github.com/DynamoDS/Dynamo/pull/2196.

### Reviewers

@Benglin, please take a look.
The comment below is not necessary, its purposes are clear, simplify it as:

```cs
var searchTextEmpty = string.IsNullOrEmpty(this.viewModel.SearchText);
libraryView.Visibility = searchTextEmpty ? Visibility.Visible : Visibility.Collapsed;
```