nitcorn: use a default virtual host when none are configure to handle a request

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
nitcorn: add the receiving virtual host to `answer`

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
nitcorn: by default a file is an application/octet-stream

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tnitter: redirect after posting

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>