Refresh command needs an icon

[Brother Gabriel-Marie]

I am a mousey kind of user, so I added the Refresh (cmd_refreshThumb) button to my toolbar.

But it doesn't have any associated icon, and since it is a built-in command, the parameter buttons are disabled for it (Set label..., Set Icon...).

In fact, I think that for the built-in commands, the "Set label..." and "Set Icon..." buttons should be enabled so the user can customize them.

(There seems to be a way to personally customize the icons as in this thread)