Add support for JPEG ExtendedXMP

[The parser](https://github.com/AurelienLourot/image/blob/master/src/Format/JPEG.php#L330) currently assumes that the entire XML is contained in one segment, however a segment is limited to 64KB, see XMP Specification part 3. In rare instances, the XML may be longer than 64KB and require to be splitted according to the ExtendedXMP definition.