Add ol.style.Icon#getImageSize
Add write support to KML format
Add export button to kml example
Add an exampleNS.strToBase64 function

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Base64_encoding_and_decoding
Use exampleNS.strToBase64 in kml example
Minor change to the example externs file
Create valid KML documents

Thanks @bartvde.
Use ol.xml.setAttributeNS for xmlns attributes
Fix nodes order in Placemark and IconStyle
Add ol.format.KML.SCHEMA_LOCATION_
Add ol.format.XSD.writeBooleanTextNode
Remove the unused ol.format.KML.DOCUMENT_SEQUENCE_
Merge pull request #2244 from elemoine/kmlwrite

KML write support