tools (common/template): changed blog_date filter to date_days

Instead of returning the whole sentence, date_days only return the number of days between now and the given timestamp.
This way the template author can choose how to use it, and translation can be done template side.

src/tools/common/template.py

@@ -195,7 +195,7 @@ class Renderer(object):
         # custom filters
         self.env.filters['next_gidx'] = self._next_gidx
         self.env.filters['cur_gidx'] = self._cur_gidx
-        self.env.filters['blog_date'] = self._blog_date
+        self.env.filters['date_days'] = self._date_days
 
     def installTranslations(self):
         i18n_dir = os.path.join(self.base_dir, 'i18n')
@@ -319,9 +319,8 @@ class Renderer(object):
         """Use current current global index as suffix"""
         return u"{}_{}".format(value, ctx['gidx'].current())
 
-    def _blog_date(self, timestamp):
-        # FIXME: Q&D, need to be done properly
-        return unicode(int(time.time() - int(timestamp))/(3600*24)) + u" days ago"
+    def _date_days(self, timestamp):
+        return int(time.time() - int(timestamp))/(3600*24)
 
     def render(self, template, theme=None, locale=DEFAULT_LOCALE, root_path=u'', css_files=None, css_inline=False, **kwargs):
         """render a template