Add 'do not use' warning to view.setProjection

[ci skip]
Merge pull request #1146 from probins/setproj

Add 'do not use' warning to view.setProjection
Improve handling of error responses from Bing

Previously goog.asserts.assert was used to check that the response was
successful, which are stripped from compiled code.  This commit sets the
ERROR state on the source instead.
Merge pull request #1149 from twpayne/bing-maps-errors

Improve handling of error responses from Bing
Check resources length of first resource set (see #1149)
Use permanent Bing Maps API key

This key is registered for "Not-for-Profit" use by OpenLayers as a project of OSGeo - 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.
Merge pull request #1150 from tschaub/bing

Use permanent Bing Maps API key.
Some additions to View2d docs
[ci skip]
Merge pull request #1151 from probins/viewdocs

Some additions to View2d docs
Export ol.extent.createEmpty function
Merge pull request #1159 from twpayne/export-create-empty

Export ol.extent.createEmpty function
Merge remote-tracking branch 'upstream/master'