update pdfbox to a version compatible with XWiki 5.4.4

 also avoid installing the pdfbox jars (and others)
which are already present on the servlet container
and fix conflict on .gitignore
update documentation to XWiki version 5.4.4
Merge pull request #2 from espresto/xwiki-544-test

XWiki 5.4.4 update pdfbox