Add target/sourceProjection to ol.format.Feature#read*
Add target/sourceProjection to ol.format.JSONFeature#read*
Add target/sourceProjection to ol.format.GeoJSON#read*
Use a ReadFeatures object instead of sourceProjection/targetProjection
Update read* signatures in ol.format.JSONFeature to use options
Introduce WriteOptions for feature formats
Add write transform capability to ol.format.JSONFeature
Implement write transforms for ol.format.GeoJSON
Make projection retrieval consistent
Better descriptions of options
Add transformGeometry function to avoid repeated code
Get projection from data if dataProjection is not specified
Add transform tests for GeoJSON readFeatures
Add ReadOptions and WriteOptions for XML formats
Implement ReadOptions and WriteOptions for ol.format.GML
Make options complete in ol.format.Feature already
Add GeoJSON tests for write transforms
Implement GML.readProjectionFromNode()
Fix GeoJSON.readFeaturesFromObject

Only feature collections worked properly.
Implement read transforms for ol.format.TopoJSON