Use multi-file upload for "images" field

Closes #62

apps/map/migrations/0065_casestudy_images.py

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.6 on 2018-05-26 15:47
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('files', '0003_auto_20180526_1547'),
+        ('map', '0064_auto_20180526_1536'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='casestudy',
+            name='images',
+            field=models.ManyToManyField(blank=True, related_name='image_for', to='files.ImageFile', verbose_name='Images'),
+        ),
+    ]

apps/map/migrations/0066_copy_images_to_imagefiles.py

@@ -0,0 +1,36 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.6 on 2018-05-26 15:48
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+def copy_images(apps, schema_editor):
+    CaseStudy = apps.get_model('map', 'CaseStudy')
+    ImageFile = apps.get_model('files', 'ImageFile')
+    User = apps.get_model('auth', 'User')
+
+    for case_study in CaseStudy.objects.all():
+        author = case_study.author
+        if author is None:
+            author = User.objects.get(username='root')
+
+        imagefile = ImageFile(
+            file=case_study.image,
+            caption=case_study.image_caption,
+            credit=case_study.image_credit,
+            user=author
+        )
+        imagefile.save()
+        case_study.images.add(imagefile)
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('map', '0065_casestudy_images'),
+    ]
+
+    operations = [
+        migrations.RunPython(copy_images, migrations.RunPython.noop),
+    ]

apps/map/migrations/0067_remove_old_images.py

@@ -0,0 +1,27 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.6 on 2018-05-29 05:20
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('map', '0066_copy_images_to_imagefiles'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='casestudy',
+            name='image',
+        ),
+        migrations.RemoveField(
+            model_name='casestudy',
+            name='image_caption',
+        ),
+        migrations.RemoveField(
+            model_name='casestudy',
+            name='image_credit',
+        ),
+    ]