linux-initrd: Add modules for ATA controllers by default.

Reported by th3kent on #guix.

* gnu/system/linux-initrd.scm (base-initrd)[linux-modules]: Add
  pata_acpi.ko and pata_atiixp.ko.

gnu: Introduce (gnu artwork) module.

* gnu/artwork.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.
* gnu/services/xorg.scm: Use it.
  (%artwork-repository): Remove.
* gnu/system/grub.scm: Use it.
  (%artwork-repository): Remove.

services: Add 'auto-start?' field to <service>.

* gnu/services.scm (<service>)[auto-start?]: New field.
* gnu/services/dmd.scm (dmd-configuration-file): Honor it.
* gnu/system/install.scm (cow-store-service): Add 'auto-start?' field.

doc: Mention "audio" and "video" groups in configuration template.

* gnu/system/os-config.tmpl (users): Add "audio" and "video" groups and
  explain.

services: Add 'user-unmount-service' as an essential service.

* gnu/services/base.scm (user-unmount-service): New procedure.
* gnu/system.scm (essential-services): Use it.
* gnu/system/install.scm (cow-store-service): Mention it in comment.

install: Add GRUB to the set of global packages.

* gnu/system/install.scm (installation-os)[packages]: Add GRUB.

system: grub: Adjust default theme color.

* gnu/system/grub.scm (%default-theme)[color-highlight]: Change
  foreground to cyan, as suggested by Felipe López.

system: grub: Add preliminary support for themes.

* gnu/system/grub.scm (<grub-image>, <grub-theme>): New record types.
  (%artwork-repository, %background-image): New variables.
  (<grub-configuration>)[theme]: New field.
  (svg->png, resize-image, grub-background-image, eye-candy): New
  procedures.
  (grub-configuration-file): Use 'eye-candy' and add it in BUILDER.

vm: The 'run-vm' scripts now passes its arguments to QEMU.

* gnu/system/vm.scm (system-qemu-image/shared-store-script): Add "$@" at
  the end of the script.
  (common-qemu-options): Remove trailing newline.
* doc/guix.texi (Invoking guix system): Document it.

vm: Fix 'vm --full-boot' to produce a sufficient disk image.

* gnu/system/vm.scm (system-qemu-image/shared-store): Add
  #:disk-image-size and #:full-boot? parameters and honor them.  Pass
  '#:copy-inputs? full-boot?', and change #:inputs argument.
* guix/scripts/system.scm (system-derivation-for-action): Pass
  #:disk-image-size to 'system-qemu-image/shared-store'.
* doc/guix.texi (Invoking guix system): Mention use of '--image-size' in
  conjunction with '--full-boot'.

vm: Support 'guix system vm --full-boot'.

* gnu/system/vm.scm (system-qemu-image/shared-store-script): Add
  #:full-boot? parameter and honor it.
* guix/scripts/system.scm (system-derivation-for-action): Likewise.
  (perform-action): Likewise.
  (show-help): Document '--full-boot'.
  (%options): Add '--full-boot'.
  (guix-system): Add #:full-boot? argument in call to 'perform-action'.
* doc/guix.texi (Invoking guix system): Document it.

vm: Factorize common QEMU options.

* gnu/system/vm.scm (common-qemu-options): New procedure.
  (system-qemu-image/shared-store-script): Use it.

vm: Remove unused procedure.

* gnu/system/vm.scm (input->name+output): Remove.  Its last user
  disappeared in commit b53833b.

vm: Disable swap devices in virtualized OSes.

* gnu/system/vm.scm (virtualized-operating-system): Add 'swap-devices'
  field.

linux-initrd: Adjust VM code and doc to new 'base-initrd' signature.

This fixes regressions introduced in de1c158 ("system: Add support for
boot-time mapped devices.").

* doc/guix.texi (Initial RAM Disk): Adjust example with custom use of
  'base-initrd'.  Document #:mapped-devices parameter of 'base-initrd'.
* gnu/system/vm.scm (system-disk-image, system-qemu-image,
  virtualized-operating-system): Adjust call to 'base-initrd' to new
  signature.

system: Add support for boot-time mapped devices.

* gnu/build/linux-boot.scm (boot-system): Add #:pre-mount parameter and
  honor it.
* gnu/system/linux-initrd.scm (base-initrd): Add #:mapped-devices
  parameter.  Add 'device-mapping-commands' variable, and use it to
  build the #:pre-mount argument of 'boot-system'.
* gnu/system.scm (mapped-device-user,
  operating-system-user-mapped-devices,
  operating-system-boot-mapped-devices): New procedures.
  (device-mapping-services): Use 'operating-system-user-mapped-devices'
  instead of 'operating-system-mapped-devices'.
  (operating-system-initrd-file): Call the initrd with #:mapped-devices.

system: Add udev rule for /dev/kvm.

* gnu/services/base.scm (kvm-udev-rule): New procedure.
  (udev-service): Use it, and add it to RULES.
  (guix-build-accounts): Add "kvm" to the 'supplementary-groups' field.
* gnu/system/shadow.scm (%base-groups): Add "kvm".

linux-initrd: Remove now obsolete #:guile-modules-in-chroot? parameter.

* gnu/build/linux-boot.scm (boot-system): Remove
  #:guile-modules-in-chroot? and related code.
* gnu/system/linux-initrd.scm (base-initrd): Likewise.
* gnu/system/vm.scm (expression->derivation-in-linux-vm): Remove
  #:guile-modules-in-chroot? argument in 'base-initrd' call.

system: Define 'device-mapping-kind', and add a 'close' procedure.

* gnu/system/file-systems.scm (<mapped-device-type>): New record type.
  (<mapped-device>)[command]: Remove field.
  [type]: New field.
* gnu/services/base.scm (device-mapping-service): Rename 'command'
  parameter to 'open'.  Add 'close' parameter and honor it.
* gnu/system.scm (luks-device-mapping): Rename to...
  (open-luks-device): ... this.
  (close-luks-device): New procedure.
  (luks-device-mapping): New variable.
  (device-mapping-services): Get the type of MD, and pass its 'open' and
  'close' fields to 'device-mapping-service'.

system: Add "input" to '%base-groups'.

* gnu/system/shadow.scm (%base-groups): Add "input" group.