More improvements for scheduling

• Show tooltips with AK details for unscheduled AK Slots, too
• Show current name of day in day views of scheduling
• Introduce possibility to mark an AK Slot as fixed

AKModel/migrations/0042_akslot_fixed.py

+# Generated by Django 3.0.6 on 2020-11-04 23:31
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('AKModel', '0041_constraint_violation'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='akslot',
+            name='fixed',
+            field=models.BooleanField(default=False, help_text='Length and time of this AK should not be changed', verbose_name='Scheduling Fixed'),
+        ),
+    ]