emacs: Add missing (require 'guix-profiles).

Reported by Christopher Allan Webber <cwebber@dustycloud.org> on #guix.

Several modules use the code from 'guix-profiles' without requiring it.  It
was never noticed before commits e4e2154644
and 13fe4891fa, because 'guix-emacs' required
this module.  But now, when 'site-start.el' loads 'guix-emacs',
'guix-profiles' may not exist yet, so it may not be required.  This will
lead to an error when some of "M-x guix-..." commands will be used.  See
<https://gnunet.org/bot/log/guix/2016-02-03#T898859>.

* emacs/guix-base.el: Require 'guix-profiles'.
* emacs/guix-ui.el: Likewise.
* emacs/guix-ui-generation.el: Likewise.
* emacs/guix-ui-package.el: Likewise.

emacs/guix-base.el

@@ -30,6 +30,7 @@
 (require 'guix-read)
 (require 'guix-utils)
 (require 'guix-ui)
+(require 'guix-profiles)
 
 (defgroup guix nil
   "Settings for Guix package manager and friends."

emacs/guix-ui-generation.el

@@ -35,6 +35,7 @@
 (require 'guix-guile)
 (require 'guix-entry)
 (require 'guix-utils)
+(require 'guix-profiles)
 
 (guix-ui-define-entry-type generation)
 

emacs/guix-ui-package.el

@@ -37,6 +37,7 @@
 (require 'guix-hydra-build)
 (require 'guix-read)
 (require 'guix-license)
+(require 'guix-profiles)
 
 (guix-ui-define-entry-type package)
 (guix-ui-define-entry-type output)

emacs/guix-ui.el

@@ -30,6 +30,7 @@
 (require 'guix-guile)
 (require 'guix-utils)
 (require 'guix-messages)
+(require 'guix-profiles)
 
 (guix-define-groups ui
   :group-doc "\