Library prototype standard panel

Standard panel has been added. However, it crashes application at first time, when user click on class button. To avoid it sliderBar should be drag at th left side.
I'm not thinking too much about this for now (in the middle of a meeting), but if we can get rid of this converter, then we should go for it (just like another review comment I left in another PR for ```LibraryWrapPanelWidthConverter``` to use a ```Grid```).