Allow tileLoadFunction override for ol.source.OSM
Allow tileLoadFunction override for ol.source.BingMaps
Allow tileLoadFunction override for ol.source.TileJSON
Allow tileLoadFunction override for ol.source.TileWMS
Allow tileLoadFunction override for ol.source.WMTS
Allow tileLoadFunction override for ol.source.Stamen
Allow tileLoadFunction override for ol.source.MapQuestOSM and MapQuestOpenAerial
Merge pull request #1044 from fredj/tileLoadFunction_override

Allow tile load override for all ol.source.TileImage based classes