#280: workaround wrong order of optional/nullable parameters

[superbiche]

Fixes https://github.com/WsdlToPhp/PackageGenerator/issues/280

[mikaelcom]

@superbiche You need to update the genereted files used for tests. The simpliest way is to:

1. uncomment line https://github.com/WsdlToPhp/PackageGenerator/blob/develop/tests/File/AbstractFile.php#L56
2. launch locally phpunit on tests/File/StructTest.php
3. comment back line https://github.com/WsdlToPhp/PackageGenerator/blob/develop/tests/File/AbstractFile.php#L56
4. commit and push the updated files

Thx