Show wallets icon with no link and no name instead of the question mark icon

A few bitcointalk users reported that they didn't think that the current hidden wallets were hidden wallets. To make this more obvious, someone on the Bitcoin Foundation forum suggested to use grey icons of each wallet. This pull request allows this.

Since each wallet names and links remain unavailable before the user click the warning, it seems like a good way to do it. Any more opinions?

Edit : Using the full color icon with no name and no link seems more intuitive.

![Capture du 2013-04-08 15:23:16](https://f.cloud.github.com/assets/3578089/353454/0e754148-a082-11e2-936f-ef97826123da.png)