Be more consistent with useTile abstract method
Merge pull request #359 from bbinet/useTile-consistent

Be more consistent with useTile parent method
Using a server that is not down

fix #353
Merge pull request #360 from ahocevar/demo_dot_opengeo_dot_org

Using a server that is not down. r=@elemoine
Add ol.source.BingMaps.getStyle function
Export ol.layer.*.getSource function
Add a basic layer selector in bing-maps example