Make email CSV column order and headers configurable

[wagner-intevation]

[wagner-intevation]

For example:

CSV input file contains: server_hk, user, ip, port, timestamp, key_hash
Assigned to the IntelMQ fields: extra.hostkey, extra.user, source.ip, source.port, time.source, extra.key_hash
Then, the ASN-Lookup adds source.asn

Fields to be sent could be:
source.asn as "asn", source.ip as "ip", time.source as "timestamp", source.port as "port", extra.user as "user" and "extra.key_hash" as "key_hash"

[wagner-intevation]

Currently, all selected columns will be sent in the emails' data:

intelmq-webinput-csv/intelmq_webinput_csv/serve.py

Line 515 in 37c0ba6

format_spec = build_format_spec(body.get('assigned_columns'))

The user needs a UI to build this "table format" by making the assignment of column name and field name. It could be placed in the "Send notifications" section below the Templates section under a new heading "Table format".
The default format would be the current behaviour: all assigned columns

At each call to the process and mailgen preview calls, the clients needs to add the table format (identical to the template body itself).

Maybe the administator should be able to set a different default, but that's not yet decided.