Add ElasticSearch reindex command

src/documents/management/commands/reindex.py

+#!/usr/bin/env python3
+from django.core.management.base import BaseCommand
+from images.models import Image
+
+
+class Command(BaseCommand):
+    help = 'Fully reindex all transcriptions into ElasticSearch'
+
+    def handle(self, *args, **options):
+        nb = Image.objects.count()
+        last = 0
+        for i, img in enumerate(Image.objects.all()):
+            percent = int(100.0 * (i + 1) / nb)
+            if percent % 5 == 0 and last != percent:
+                print('{0: >3}% => {1: >5} / {2}'.format(percent, i, nb))
+                last = percent
+            img.index()