Update DOCTYPE notation in jade template
Extract code for graceful server shutdown
WIP: busboy-test; dispatch-function not working
Prefix tests with filenames
Use busboy instead of express.multipart/express.urlencoded

Unfortunately, this is a rather huge commit because everything was so entangled.
To break it down:

- Use busboy instead of express.multipart/express.urlencoded
  (will be removed in future Express versions)
- Split dispatch method in dispatchGET and dispatchPOST: Busboy/file uploads
  work only with POST, no need to clutter the GET route as well
- Extract default error responses
- Make callback structure a bit cleaner, try to get rid of additional
  'param' arguments
- File upload: Add limits for filesize, cancel upload of files with wrong
  mime type (force HTTP connection to close)
Extract application config values

Additionally, I switched to YAML for configuration. It may sound trivial, but I really love the ability to add comments. On top of this, the syntax is much cleaner.
Catch errors on server shutdown

Ran into this strange case that the shutdown function may be called twice on rare occasions when hitting Ctrl^C.
For production, better be safe than stacktrace.
Just moving things around a bit
Check for query parameters being strings

Prevents HTTP Parameter Pollution (HPP), e.g. ?directinput=foo&directinput=bar
The field limit and boolean flag for Busboy take care of this for POST requests
already.
Improve logging settings
Fix require-yaml path