fix wacom hotplug and all Intuos 5 issues

- drop custom config:
  (please wacom using folks review this part and think
  about how to get it back if its important to you)

- put default config shipping with  xf86_input_wacom
  into /etc/X11/xorg.conf.d/
  which seems to be interpreted again when
  devices are hot plugged

- when starting x11, also provide xinput
  .. you never know when you need it

This fixes all problems I had:
- device only worked when plugged in, then xorg was started
(an alternative quick fix is switching to terminal by ctrl-alt-F1 and back)
- I had to disable some devices, because eg myaint switched input
device many times a sec rendering it unusable otherwise, some of those devices
configured did not work.

Details:
http://sourceforge.net/apps/mediawiki/linuxwacom/index.php?title=FAQ#Is_hotplugging_supported_for_my_USB_tablet.3F
See 12 -> HAL or xorg.conf.d
KDE: fix config build when grub is used to generate boot menu, but isn't used as a loader.
Add NixOS Manual build instructions to itself.
nixos-checkout: fix output if ran with no options, -h and --help. Other options will still trigger
mkdir output :(
nixos-checkout: let it run without args again.
Manual: improve source checkout section
Merge pull request #154 from MarcWeber/submit/x11-wacom-intuos5-fix

fix wacom hotplug and all Intuos 5 issues
try to fix zfs into initrd