New bulk printing features

[Jacopo Cappellato]

As of rev. 521619 there is now the ability to submit an async print 
request for many document (rendered from a screen definition with fop) 
and send it to a (laser, for now) printer.
You can test it by selecting the "Print" option in the find order list 
screen. You can optionally select a printer from the drop down box.
If no printer is selected the system will select the first that the 
server's JVM can locate (so it must be defined in the server where OFBiz 
is running, even if it is a lan printer).

Let me know what you think (I did very few test, also with the help of 
David Shere), and I know that a lot can be done to improve these feature.

Jacopo