handle custom service name with space more gracefully

```
What steps will reproduce the problem?
1. add a custom service via ~/.core/myservices/
2. use a space in the new service name
3. connect GUI, click on a node's services, use wrench icon for new service
4. obscure GUI exception is shown

What is the expected output? What do you see instead?

Should show dialog box: "invalid custom service name: cannot contain spaces" or
use proper quoting so this can be supported.
```

Original issue reported on code.google.com by `ahrenh...@gmail.com` on 24 Jul 2014 at 5:41