series: Add a plural form for series

That makes the admin interface nicer to read instead of 'Seriess'.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>

patchwork/migrations/0017_series_meta.py

@@ -0,0 +1,18 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('patchwork', '0016_add_delegation_rule_model'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='series',
+            options={'verbose_name_plural': 'Series'},
+        ),
+    ]

patchwork/models.py

@@ -556,6 +556,9 @@ def filename(self):
     def __str__(self):
         return self.name
 
+    class Meta:
+        verbose_name_plural = 'Series'
+
 # Signal one can listen to to know when a revision is complete (ie. has all of
 # its patches)
 series_revision_complete = django.dispatch.Signal(providing_args=["revision"])