Create PDF Renderer

To be decided if we use:

• the same mechanism as currently used: http://tinyurl.com/5em7sb
• the Doxia FO module (it generates XSL-FO which we then need to convert to PDF using Apache FOP)
• we rewrite the Renderer from scratch using iText directly (we create event using the iText API directly). One caveat: we need to find how we'll transform XMLBlock events into PDF using this method. The current mechanism transforms to HTML before converting to XSL-FO thus solving this issue

Note: This is minor since the current mechanism works. This is a refactoring to use the new Renderer mechanism.