* [react-router] add RouteComponentProps.staticContext
* [react-router] revert RouteConfig test file
* [react-router] Add example for StaticRouter and staticContext
SwitchProps.children is too strict for projects using typescript 2.3.
With typescript 2.3 the children could be made mandatory, but this will
break backwards compatibility with any ts 2.2 user
The `Router` component passes a context object down to children. This
commit adds the type definition for this context object for children of
`Router` to use.
