[MERGE] babel: use babel for locale-aware read_group date formatting.

When grouping on a date or datetime field, read_group groups by (year, month),
and formats that pair to have a displayable result (as a group title).

This is currently done with strftime and the pattern `%B %Y` (complete word
month, long year), which is problematic as — at best — it uses the server's
locale for its formatting. This means if the server works in an english locale
e.g. russian users are going to see the month name in english, instead of their
own language.

This proposal makes use of `babel.dates.format_date`, which is locale-aware
(and to which a locale can be provided directly) and the locale present in the
request context to format the month, year pair according to the user's
language.

bzr revid: vmt@openerp.com-20121012144634-spaqze7d4jc8l00l

openerp/osv/orm.py

@@ -41,6 +41,7 @@
 
 """
 
+import babel.dates
 import calendar
 import collections
 import copy
@@ -2701,7 +2702,9 @@ class BaseModel(object):
                     dt = datetime.datetime.strptime(alldata[d['id']][groupby][:7], '%Y-%m')
                     days = calendar.monthrange(dt.year, dt.month)[1]
 
-                    d[groupby] = datetime.datetime.strptime(d[groupby][:10], '%Y-%m-%d').strftime('%B %Y')
+                    date_value = datetime.datetime.strptime(d[groupby][:10], '%Y-%m-%d')
+                    d[groupby] = babel.dates.format_date(
+                        date_value, format='MMMM yyyy', locale=context.get('lang', 'en_US'))
                     d['__domain'] = [(groupby, '>=', alldata[d['id']][groupby] and datetime.datetime.strptime(alldata[d['id']][groupby][:7] + '-01', '%Y-%m-%d').strftime('%Y-%m-%d') or False),\
                                      (groupby, '<=', alldata[d['id']][groupby] and datetime.datetime.strptime(alldata[d['id']][groupby][:7] + '-' + str(days), '%Y-%m-%d').strftime('%Y-%m-%d') or False)] + domain
                 del alldata[d['id']][groupby]