[O] new syntax of completion and preparation functions for publishing

[Julien Cubizolles]

According to ORG-NEWS:

"Preparation and completion functions are now called with an argument,
which is the project property list. It used to be dynamically scoped
through the ~project-plist~ variable."

I'd like to try to improve on my configuration of projects but I'm
unsure hot to use this new feature. How do you use it ?

Julien.