previewer: pdfjs intergration preparation

* Fixes problem with pdftk bundle naming collision.

* Introduces minor changes in zip previwer.

* Fixes problem with jquery loading in records module.

Signed-off-by: Adrian Pawel Baran <adrian.pawel.baran@cern.ch>
previewer: pdfjs viewer

* Adds pdfjs viewer.

Signed-off-by: ©Mozilla <https://github.com/mozilla/pdf.js/>
previewer: custom invenio viewer

* Customize the pdfjs viewer for invenio.

Signed-off-by: Adrian Pawel Baran <adrian.pawel.baran@cern.ch>