fix #58 - Export PDF : update artifact in pom files

I tested and the PDF export works.

@jkowalczyk @mfaure could you review this patch ? if it's is Ok for you, I myself manage the merge.

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log "mvn clean install"

[WARNING] The artifact com.lowagie:itext:jar:4.2.1
has been relocated to com.itextpdf:itextpdf:jar:5.5.*

same information to following URL http://mvnrepository.com/artifact/com.lowagie/itext/4.2.