Added pdf merge functionality. Also added extra conditions to the clone object.

Added the ability to merge multipe pdfs into one. Code based on the forum answer:
https://mxforum.mendix.com/questions/2158/Is-it-possible-to-print-multiple-documents-at-once. I built this into the community commons because Mo from LV asked this question: https://mxforum.mendix.com/questions/7057/Combine-many-pdfs-into-one-.

Also added extra conditions to the clone object to prevent errors when cloning an auto nnumber.