Getting ready for heroku
Added css file, and first try to solve the hosting problem
fixed logging, fixed incorrect static URL
Added favicon handler
Refactored startup model
disabled MAJ chars in random string generation
Probably fixed
PDF download feature completed

We can now download a PDF version of the document via the <doc_id>/dl/pdf url.

This uses wkhtmltopdf, so better be sure it is present on the host.