Add permissions to user/group initializers

Thank you @bdlamprecht for researching how to add permissions to
users and groups in #92.

Fixes #92

initializers/groups.yml

@@ -7,3 +7,10 @@
 # writers:
 #   users:
 #   - writer
+#   permissions:
+#   - add_device
+#   - change_device
+#   - delete_device
+#   - add_virtualmachine
+#   - change_virtualmachine
+#   - delete_virtualmachine