Add Schmervice types and improve server decorations

[ianjkaplan]

Schmervice types in definitely typed are a good starting point so I ported them and have added tsd type declaration tests since I prefer making explicit type assertions in tests.

I want to update the the decorator functions the to accept a string or true rather than an optional boolean since the function also take string arguments that correspond to namespaces. It would look something like the following

declare module '@hapi/hapi' {
    interface Server {
        /**
         * decorations can be passed a plugin namespace or a boolean to return all registered services
         * @param all
         */
        services: (all?: true | string) => RegisteredServices;
    }

    interface Request {
        services: (all?: true | string) => RegisteredServices;
    }

    interface ResponseToolkit {
        services: (all?: true | string) => RegisteredServices;
    }
}