New design is bound to BrowserRootCategories collection

New design is bound to BrowserRootCategories collection. There are some bugs but we have something to show. Works correctly for Geometry category. Possible too long names of some functions. For example: `Geometry.Cuboid`.

@Benglin, please review.
Does the below code work? Because what I was trying to propose was: we expect the first child to be ```StandardPanel```, so if it is **not**, then we throw the exception. Your code throws the exception when it **is** a ```StandardPanel```. Have we tested this code?