Updated from iText-1.3 to iText-5.5.1

Two java files had to be modified for this commit to compile and work:

• src-plugins/IO_/io/PDF_Writer.java: only package name changes.
• src-plugins/Colocalisation_Analysis/results/PDFWriter.java: a method that disappeared has been replaced by another one, preserving functionalities.

Signed-off-by: Jean-Yves Tinevez <jean-yves.tinevez@pasteur.fr>