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.
I understand from the ```DataTrigger``` above: when ```libraryView``` becomes visible, the ```librarySearchView``` becomes collapsed. I would recommend doing this thing differently, please create a YouTrack task for subsequent implementation:

Either one can be visible at a time: ```LibraryView``` or ```LibrarySearchView```. This is determined with a read-only ```ViewMode``` property on the ```LibraryContainerView``` class:

    ```cs
    enum ViewMode { LibraryView, LibrarySearchView };

    internal ViewMode CurrentMode { get; private set; }

    // Then we need a converter to convert this into Visibility for both the views
    class ViewModeToVisibilityConverter : IValueConverter
    {
        public object ConvertTo(..., parameter)
        {
            if ((parameter as string).Equals("LibraryView"))
                return ...;
            else if ((parameter as string).Equals("LibrarySearchView"))
                return ...;
        }
    }
    ```