Add ReportAsset model

- Files which can be embedded into a report

InvenTree/report/migrations/0003_reportasset.py

@@ -0,0 +1,22 @@
+# Generated by Django 3.0.5 on 2020-05-21 04:04
+
+from django.db import migrations, models
+import report.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('report', '0002_auto_20200521_0350'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='ReportAsset',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('asset', models.FileField(help_text='Report asset file', upload_to=report.models.rename_asset)),
+                ('description', models.CharField(help_text='Asset file description', max_length=250)),
+            ],
+        ),
+    ]