Download a file with the file name from filename attribute field

Same feature as GTK client, to do at SAO [1]

[1] http://doc.tryton.org/4.0/trytond/doc/ref/models/fields.html#trytond.model.fields.Binary.filename

added sao + 1 deleted label

If you are not going to implement the missing features of sao, please do not fill an issue.

I uploaded review33671002 which uses the filename when downloading, it's also done for reports so it also solves #6051 (closed).

assigned to @xcodinas

added type::feature + 1 deleted label and removed 1 deleted label

New review33671002 at https://codereview.tryton.org/33671002/#ps1

review33671002 updated at https://codereview.tryton.org/33671002/#ps10003

review33671002 updated at https://codereview.tryton.org/33671002/#ps30001

review33671002 updated at https://codereview.tryton.org/33671002/#ps50001

review33671002 updated at https://codereview.tryton.org/33671002/#ps90001

review33671002 updated at https://codereview.tryton.org/33671002/#ps110001

As .click is normally not supported on non-input tag according to W3C but that browsers seem to support it any way, I think we should design the feature in a way that will work in any case.
My idea is that we should always create a popup with the link to download and trigger the click (if it works or not) and close the popup on click event.
This should be done no matter if name is supported or not.

review33671002 updated at https://codereview.tryton.org/33671002/#ps130001

review33671002 updated at https://codereview.tryton.org/33671002/#ps150001

review33671002 updated at https://codereview.tryton.org/33671002/#ps170001

review33671002 updated at https://codereview.tryton.org/33671002/#ps190001

review33671002 updated at https://codereview.tryton.org/33671002/#ps210001

review33671002 updated at https://codereview.tryton.org/33671002/#ps230001

review33671002 updated at https://codereview.tryton.org/33671002/#ps250001

review33671002 updated at https://codereview.tryton.org/33671002/#ps270001