We want to distinguish the url and the url_preview. The url_preview
property will be provided only if the mimetype is listed in the
ITEM_PREVIEWABLE_MIME_TYPES settings. Also an other route is added to
nginx forcing the content-disposition with the value attachment for
download url.
This commit, with contributions from Sylvain Grizard, adds support
for PaaS deployment platforms such as Scalingo, which build the
project on commit. It uses the La Suite Buildpack, which compiles
the frontend first as static files, and serves them along with
the backend with nginx.