Move packages from com.lowagie to org.openpdf

[olivierDelierre]

Since OpenPDF has now moved their classes from com.lowagie to org.openpdf, it would be good to:

• Change the dependency from artifact openpdf to openpdf-core-modern
• Move all classes of OpenRTF from com.lowagie to org.openpdf

Main reason it to avoid facing all those deprecated tags while using both library in the mean time if using the old packages.

[andreasrosdal]

It was done here: 0743bd0

Now we just need a new maven release, bitte. @fridrich