Update key in bing-maps example

Key information:

```
OpenLayers Trial/Windows Store
Ar33pRUvQOdESG8m_T15MUmNz__E1twPo42bFx9jvdDePhX0PNgAcEm44OVTS7tt
Update Trial / Windows Store app
Created Date: 07/17/2013      Expiration Date: 10/15/2013
```

I had to create an "Update Trial / Windows Store app" key - the bing maps site refused that I create another "Trial / Public website" key for my account. Though the key seems to work, I'm not sure it's appropriate.

Also, my bing maps account has this message:

```
You have created the maximum of 3 keys for this account. Once a key is created, you cannot delete
the key or change the key type or application type. If you require additional keys, you may need a
licensed account. For information on licensing, please contact us.
```

So I'm not sure I'll be able to renew the key the next time it's expiring.