Use permanent Bing Maps API key

This key is registered for "Not-for-Profit" use by OpenLayers as a project of [OSGeo](http://www.osgeo.org/content/foundation/about.html) - a 501(c)(4) organization.  See the complete [Terms of Use](http://www.microsoft.com/maps/product/terms.html) under the Eduction or Non-Profit Organization Use section.

In addition, e70b55b60bf24f12f24c50458bbe758a86f6c0be avoids setting the error state for valid API keys.