doc: Fix misuses of @ref.

* doc/guix.texi (Invoking guix-daemon, Features, Invoking guix download,
  Invoking guix refresh, GNU Distribution, Package Modules, Packaging
  Guidelines, Package Naming): Replace misuses of @ref with @xref or
  @pxref.

doc: Suggest using 'guix pull' before 'guix system reconfigure'.

* doc/guix.texi (Invoking guix system): Suggest running 'guix pull'
  before the first use of 'guix system reconfigure'.

doc: Document --key-download option of 'guix refresh'.

* doc/guix.texi (Invoking guix refresh): Document --key-download.

doc: Document "guix import".

* doc/guix.texi (Requirements): Add xref to "Invoking guix import".
  (Defining Packages): Likewise.  Remove footnote about Nixpkgs
  imports.
  (Invoking guix import): New section.

doc: Fix Hydra URL.

Reported by John Darrington <john@darrington.wattle.id.au>.

* doc/guix.texi (Packaging Guidelines): Fix hydra.gnu.org URL.

doc: Clarify use of the 'password' field for user accounts.

Suggested by Alex Sassmannshausen <alex.sassmannshausen@gmail.com>.

* doc/guix.texi (Using the Configuration System): Remove 'password'
  field in the example.
  (User Accounts): Clarify use of the 'password' field, with links to
  the libc and Guile manuals.

doc: Improve acknowledgments.

* doc/guix.texi (Acknowledgments): Expound a bit.
* THANKS: Mention artwork; thank Felipe & Nikita.

gnu: xorg: Add SLiM theme based on work by Felipe López.

* gnu/services/xorg.scm (%artwork-repository, %default-slim-theme,
  %default-slim-theme-name): New variables.
  (slim-service): Add #:theme and #:theme-name parameters.
  [slim.cfg]: Honor #:theme-name.
  Honor #:theme by setting the "SLIM_THEMESDIR" environment variable.
* doc/guix.texi (X Window): Adjust 'slim-service' documentation
  accordingly.  Document '%default-slim-theme' and
  '%default-slim-theme-name'.

activation: Set the firmware search path.

* gnu/build/activation.scm (activate-firmware): New procedure.
* gnu/system.scm (<operating-system>)[firmware]: New field.
  (directory-union): New procedure.
  (%base-firmware): New variable.
  (operating-system-activation-script): Use 'directory-union', and call
  'activate-firmware'.
* doc/guix.texi (operating-system Reference): Document 'firmware'.

doc: Mention 'guix environment' in "Features"; add index entries.

* doc/guix.texi (Features): Add paragraph about 'guix environment'.
  (Build Systems): Add @cindex.
  (Invoking guix environment): Ditto.

doc: Add "GRUB Configuration".

* doc/guix.texi (operating-system Reference): Add xref to "GRUB
  Configuration".
  (GRUB Configuration): New node.

doc: Avoid @indentedblock, which is not supported by Texinfo 4.

Reported by Mark H Weaver.

* doc/guix.texi (Security Updates): Use @quotation instead of
  @indentedblock; the latter is not supported by Texinfo 4.

emacs: Add "c" key binding to copy a button link.

* emacs/guix-info.el (guix-info-button-map): New variable.
  (guix-info-button-copy-label): New procedure.
* doc/emacs.texi (Emacs Info buffer): Mention a "c" key binding.
  (Emacs Keymaps): Add 'guix-info-button-map'.

gexp: Add #:module-path parameter to 'gexp->derivation'.

* guix/gexp.scm (gexp->derivation): Add #:module-path parameter, and
  pass it to 'imported-modules' and 'compiled-modules'.
* doc/guix.texi (G-Expressions): Adjust accordingly.

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.

doc: Emphasize the availability of two user interfaces.

* doc/guix.texi (Package Management): Add a word about the two user
  interfaces.

emacs: Add 'guix-prettify'.

* emacs/guix-prettify.el: New file.
* emacs.am (ELFILES): Add it.
* doc/emacs.texi (Emacs Prettify): New node.
* doc/guix.texi (Features): Mention it.

services: xorg: Allow users to specify a list of resolutions.

* gnu/services/xorg.scm (xorg-start-command): Add #:resolutions
  parameter and 'screen-section' procedure.  Use it.
* doc/guix.texi (X Window): Adjust accordingly.