WPF - Allow setting Focus before the underlying browser has been initialized.
WPF - Allow setting Focus before the underlying browser has been initialized.

- Remove hacks from the ViewModel as Focus can now be set on Go().
- Creating a new viewmodel also sets focus

Changing tabs doesn't set focus currently.

Livit/CefSharp,Livit/CefSharp,Livit/CefSharp,Livit/CefSharp