Add proper email notifications

templates/emails/confirmation.body.txt

@@ -0,0 +1,16 @@
+Hi,
+
+You submitted a 3D print to hamlab.lt. Your codename is:
+
+    {{ submission.slug }}
+
+To put it in the queue, click the link below within 24 hours. If you don't,
+the submission (and any uploaded .stl) will be deleted automatically.
+
+    {{ confirm_url }}
+
+If you didn't submit this, you can safely ignore this email -- nothing
+happens until you click the link.
+
+— hamprint
+{{ site_url }}