Use multi-file upload for "images" field

Closes #62

apps/files/migrations/0003_auto_20180526_1547.py

@@ -0,0 +1,36 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.6 on 2018-05-26 15:47
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('files', '0002_file_user'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='ImageFile',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('file', models.FileField(upload_to='.')),
+                ('caption', models.CharField(default=None, max_length=240, null=True, verbose_name='Image caption')),
+                ('credit', models.CharField(default=None, max_length=240, null=True, verbose_name='Image credit')),
+                ('user', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='imagefile', to=settings.AUTH_USER_MODEL)),
+            ],
+            options={
+                'abstract': False,
+            },
+        ),
+        migrations.AlterField(
+            model_name='file',
+            name='user',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='file', to=settings.AUTH_USER_MODEL),
+        ),
+    ]