[FIX] website_blog: fix navlist date/filter/order

Before this fix, the tz was ignored in the search. So the group by counter
was not especially the number of blog post displayed.

The month display was wrong, date_begin was localized.
Start was eg (in Europe/brussels) : 10/31/2016 22:00:00.
So if we don't localize this time with babel, we got October as displayed
month instead of November

The Archive was not sorted by year desc, now it is.
Old behaviour was strange:
    2015: December, Octobre
    2016: December, Octobre
    => Year asc, Month desc

addons/website_blog/controllers/main.py

@@ -4,6 +4,9 @@
 import json
 import werkzeug
 import itertools
+import pytz
+import babel.dates
+from collections import OrderedDict
 
 from odoo import http, fields, _
 from odoo.addons.website.controllers.main import QueryURL
@@ -29,13 +32,20 @@ class WebsiteBlog(http.Controller):
             (r, label) = group['post_date']
             start, end = r.split('/')
             group['post_date'] = label
-            group['date_begin'] = fields.Date.to_string(self._to_date(start))
-            group['date_end'] = fields.Date.to_string(self._to_date(end))
-            group['month'] = self._to_date(start).strftime("%B")
-            group['year'] = self._to_date(start).strftime("%Y")
-        return {year: [m for m in months] for year, months in itertools.groupby(groups, lambda g: g['year'])}
+            group['date_begin'] = start
+            group['date_end'] = end
+
+            locale = request.context.get('lang', 'en_US')
+            start = pytz.UTC.localize(fields.Datetime.from_string(start))
+            tzinfo = pytz.timezone(request.context.get('tz', 'utc') or 'utc')
+
+            group['month'] = babel.dates.format_datetime(start, format='MMMM', tzinfo=tzinfo, locale=locale)
+            group['year'] = babel.dates.format_datetime(start, format='YYYY', tzinfo=tzinfo, locale=locale)
+
+        return OrderedDict((year, [m for m in months]) for year, months in itertools.groupby(groups, lambda g: g['year']))
 
     def _to_date(self, dt):
+        # TODO remove me in master/saas-14
         return fields.Date.from_string(dt)
 
     @http.route([