lazy middleware

[tanner0101]

• creates one set of middleware per event loop, preventing race conditions in middleware
• losslessly optimizes DateMiddleware to only calculate a new RFC1123 timestamp every second
• adds a new router.grouped(MiddlewareType.self) overload for creating a route group around a middleware type that will be lazily initialized (on the event loop) when requested.

router.grouped(DateMiddleware.self).get("datetest") { req in
    return HTTPStatus.ok
}

In the above snippet, DateMiddleware won't be initialized until the first time that route is hit. It will subsequently be initialized for each event loop, until all event loops have one cached.

• adds application-wide timeout for requests taking longer than 30 seconds

[ ERROR ] Vapor.VaporError.timeout: The application timed out waiting for response. (Services+Default.swift:207)
[ DEBUG ] Suggested fixes for Vapor.VaporError.timeout: Inspect the route responsible for responding to GET /fcm (EngineServer.swift:198)

Resolves #1479.