quick fix on pdf renderer
first specifications on the feature
Merge branch 'ass/jc_pim-3161' into ass/jc_3165

* ass/jc_pim-3161:
  Add or modify comments
  Refactor the PDF generation behaviour into a separate bundle
  fix style and html
  PIM-3162 : replace slik/dompdf-bundle by the library and wrap directly in the builder
Merge pull request #1489 from akeneo/ass/jc_3165

Ass/jc 3165