FEAT: Add a fifteen min cooldown between emails to admins

Probably not the right way to go about it...but it does work!

TODO: How to handle cooldown-emailing shared mailbox addresses?

RIGS/migrations/0038_profile_last_emailed.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.0.13 on 2020-01-25 01:48
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('RIGS', '0037_auto_20200111_1829'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='profile',
+            name='last_emailed',
+            field=models.DateTimeField(blank=True, null=True),
+        ),
+    ]