Rework 'xinput list' code

* Drop the questionable --loop option
* Add a --long option (opposite of --short)
* Make --short the default if no device argument is given
* XI2: Make it possible to query a single device

Signed-off-by: Thomas Jaeger <ThJaeger@gmail.com>
squashed in a man page update for --short and --long.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>