Factor out ol.TileCoordTransformType
Add ol.source.TileImage#setTileUrlFunction
Add ol.source.XYZ#setUrl and friends
Add XYZ set URL example
Add FIXME about avoiding tile cache clears
Merge pull request #1011 from twpayne/set-url

Add ol.source.XYZ#setUrl
Rename file for ol.source.TileImage
Rename options type for ol.source.TileImage