Create styles only once
Merge pull request #1647 from openlayers/style-

Create styles only once
Fix vector examples
Merge pull request #1648 from elemoine/1648

Vector examples are broken
Icon images are handled by a separate class
Fix the kml format tests
Vector renderer uses new image style interface
Vector image source uses new image style interface
Introduce an icon image cache
Use the icon image cache
Add ol.renderer.Map#scheduleExpireIconCache
Use ol.renderer.Map#scheduleExpireIconCache
Factor out icon image loading code
Remove a FIXME
Add tests for ol.renderer.vector
Add tests for ol.style.IconImageCache