Add permissions to user/group initializers

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

Fixes #92

initializers/users.yml

@@ -4,3 +4,10 @@
 #   password: reader
 # writer:
 #   password: writer
+#   permissions:
+#   - add_device
+#   - change_device
+#   - delete_device
+#   - add_virtualmachine
+#   - change_virtualmachine
+#   - delete_virtualmachine