Update copyright in documentation

Use range() instead of building the list manually. Keeps the code
shorter starting next year.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>
Reviewed-and-lolled-by: Iustin Pop <iustin@google.com>

doc/conf.py

@@ -46,7 +46,7 @@ master_doc = "index"
 
 # General information about the project.
 project = u"Ganeti"
-copyright = u"2006, 2007, 2008, 2009, 2010, 2011, 2012, Google Inc."
+copyright = u"%s Google Inc." % ", ".join(map(str, range(2006, 2013 + 1)))
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the