Add section has_stages as boolean flag

stages/migrations/0025_section_has_stages.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.6 on 2019-11-20 13:30
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stages', '0024_mark_fields_dup'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='section',
+            name='has_stages',
+            field=models.BooleanField(default=False, verbose_name='Planifie la PP sur ce site'),
+        ),
+    ]