Refactor ApolloClient instantiation to new apollo-boost syntax

[DevanB]

The advanced boilerplate has a lot of the older non-apollo-boost way of setting up the ApolloClient. For the purposes of helping others who might be new to Apollo and GraphQL, we should update this to use the new syntax.

Lines that should be refactored: L14-L56

[vivek12345]

@DevanB In here since we are using apollo-link-ws, is it possible to migrate to apollo-boost, since they still do not support websocket link in apollo-boost according to this:-
apollographql/apollo-client#3117