Process routes after middleware

[jimlambie]

This PR ensures that:

1. a request is passed through all middleware functions before the app-specific routes are examined. Prior to this a request was tested against all loaded page components at the beginning of the request, and an array of matching routes was added to the middleware stack. With this change, matching app-specific routes are looked for only if processing the middleware stack yields no valid handlers. This means that static files will be handled by serve-static before any app routes are looked up.

2. requests for static files are now passed through the request logger:

04:09:48.920Z  INFO dadi-web: GET / 200 10ms (module=router)
04:09:48.935Z  INFO dadi-web: GET /styles.css 200 5ms (module=router)
04:09:48.938Z  INFO dadi-web: GET /logo.png 200 8ms (module=router)
04:09:59.077Z  INFO dadi-web: GET /test.txt 200 3ms (module=router)
04:09:59.123Z  INFO dadi-web: GET /favicon.ico 200 2ms (module=router)

Fix #165