[downloadable] fix filename in HTTP header (closes #2522325, #2522324)
Before this changeset we use the `filename` header with utf8 encoded filename
all the time.
However RFC6266 says:
The parameters "filename" and "filename*" differ only in that "filename*"
uses the encoding defined in [RFC5987], allowing the use of characters not
present in the ISO-8859-1 character set ([ISO-8859-1]).
Therefore, we alter the code to:
1. Use `filename` and `ascii` encoding whenever possible,
2. use `filename*` with `utf8` encoding otherwise (with a filename fallback for
old browser)
We also switch the `content-disposition` value to attachement if filename is
specified, this will result as a mandatory download according to RFC6266. This
mandatory download is the expected behavior.
We changes the filename encoding to RFC5987 which is simpler, supported by all
and modern browser (including IE from version 6) and does not suffer from the
continuation issue. (see ticket #2522324 for details)
About this site
===============
This web application is based on the CubicWeb knowledge management system
from Logilab_. CubicWeb is made of an object database and a web
framework. It allows to develop an application by defining a set of
entities and their relationships, plus a set of views that present the
data selected from the object database using a specific query language.
This application has a precise schema_ and can be considered an
example of a semantic web database, as it can export the data to XML
and others formats and is not limited to publishing HTML.
Supported formats: |microformats|_ - JSON_ - |rss|_ - |dublincore|_
.. |microformats| image:: /data/microformats-button.png
.. _microformats: http://microformats.org
.. _JSON: http://www.json.org/
.. |rss| image:: /data/rss-button.png
.. _rss: http://www.rssboard.org
.. |dublincore| image:: /data/dublincore-button.png
.. _dublincore: http://dublincore.org
.. _Logilab: http://www.logilab.fr/
.. _schema: schema