Whitespaces
Moved assembling facility into a mix-in
Added the PdfCompiler compiler

This compiler allow to import PDF files directly without any processing.
Fixed compatibility with Django 1.5 (url templatetag)

Also loading the future compatibility library in order to keep
compatibility with Django 1.4.
Added the OcrPdfCompiler compiler

This compiler allow to import image-only PDF files by converting them
into tiff files and applying the same processing as for OcrTiffCompiler.
Added new compilers in default configuration file
Whitespaces