The purpose is to replace this PI with a property set in the script.
<?_wxt property name=""?>
A few default properties are available:
A property PI will expand the properety as it is defined in the script. Assume:
... <property name="theAuthor"> <author> <name>John Smith</name> <street>Elm st. 1</street> </author> </property> ...
<?_wxt property name="theAuthor"?>
will expand to:
<author> <name>John Smith</name> <street>Elm st. 1</street> </author>