Add loading to dialogs that perform some action.

• When there is a dialog that performs some action (e.g. adding new attributes to some entities) the dialogs should disable the "confirm" button, once it is clicked. Also, it should somehow display progress spinner, so it is clear that the application is working.
• This is very important because if the button is not disabled, users might send multiple actions of the same type to the backend.
• I have discovered this when I was adding some attributes in the service configuration page. It would be a good idea to check all dialogs because I think almost none of them are disabling the button this way.