MAJOR: da: Update of the DeviceAtlas API module

MAJOR: da: Update of the DeviceAtlas API module

Introduction of the new keyword about the client's cookie name
via a new config entry.

Splits the work between the original convertor and the new fetch type.
The latter iterates through the whole list of HTTP headers but first,
make sure the request data are ready to process and set the input
to the string type rightly.

The API is then able to filter itself which headers are gueninely useful,
with a special care of the Client's cookie.

[WT: the immediate impact for the end user is that configs making use of
    "da-csv" won't load anymore and will need to be modified to use either
    "da-csv-conv" or "da-csv-fetch"]