Make access level an int instead of a string.

We started with a string because we thought it could maybe provide more
flexibility, though really, an int makes much more sense, especially on
all the platforms etebase runs nowadays.

django_etebase/migrations/0027_auto_20200907_0752.py

@@ -0,0 +1,23 @@
+# Generated by Django 3.1 on 2020-09-07 07:52
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_etebase', '0026_auto_20200907_0752'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='collectioninvitation',
+            name='accessLevel',
+            field=models.IntegerField(choices=[(0, 'Read Only'), (1, 'Admin'), (2, 'Read Write')], default=0),
+        ),
+        migrations.AddField(
+            model_name='collectionmember',
+            name='accessLevel',
+            field=models.IntegerField(choices=[(0, 'Read Only'), (1, 'Admin'), (2, 'Read Write')], default=0),
+        ),
+    ]