Allow to export Spanish tax code report as files

Following https://groups.google.com/d/msg/tryton/j9gDrBTHUVE/GOI1l1ocBQAJ, it will be great to allow to export the Spanish tax code reports as file which can be uploaded to the tax authority website.

assigned to @pokoli

added accounting type::feature + 1 deleted label

Here is review45241002 which add its.

I still have to review the 303 report file as it's format is it currently generates some errors when importing in the tax authority website but it's something related to the template format and should not accept the module design.

Any comments will be very welcome.

New review45241002 at https://codereview.tryton.org/45241002/#ps1

review45241002 updated at https://codereview.tryton.org/45241002/#ps20001

review45241002 updated at https://codereview.tryton.org/45241002/#ps40001

The 303 file is now correct and uploaded correctly, so we are now ready for testing.

added 1 deleted label and removed 1 deleted label

review45241002 updated at https://codereview.tryton.org/45241002/#ps60001

review45241002 updated at https://codereview.tryton.org/45241002/#ps80001

review45241002 updated at https://codereview.tryton.org/45241002/#ps100001

review45241002 updated at https://codereview.tryton.org/45241002/#ps120001

review45241002 updated at https://codereview.tryton.org/45241002/#ps140001

review45241002 updated at https://codereview.tryton.org/45241002/#ps160001

review45241002 updated at https://codereview.tryton.org/45241002/#ps200001

review45241002 updated at https://codereview.tryton.org/45241002/#ps220001

review45241002 updated at https://codereview.tryton.org/45241002/#ps240001

review45241002 updated at https://codereview.tryton.org/45241002/#ps260001

review45241002 updated at https://codereview.tryton.org/45241002/#ps280001

review45241002 updated at https://codereview.tryton.org/45241002/#ps300001