Add support for custom output in about.py

[tdruez]

Similar to the mapping support in genabout.

When generating my csv from my About files, I'll like a custom set and order of columns.

Here's a mapping example:

name: Name
version: Version
dje_license: DejaCode License
home_url: Homepage

The output should look like:

Name	Version	DejaCode License	Homepage
name1	version1	license1	homepage1
name2	version2	license2	homepage2
...	...	...	...

[pombredanne]

Could a custom template work instead? to generate a CSV or a nicely justified list like with this?

======================= ============ ============================ ============================================================
Name                    Version      License                      Homepage
======================= ============ ============================ ============================================================
{% for about_object in about_objects -%}
{{ about_object.name.ljust(24) +}} {{ about_object.version.ljust(12) +}} {{ about_object.dje_license.ljust(28) +}} {{about_object.home_url}}
{% endfor -%}

[chinyeungli]

For some reasons, the fix in 8212969 is lost.

@DennisClark I just want to confirm that if a user provide a MAPPING.CONFIG file, ONLY the keys in the MAPPING.CONFIG will be used in the output CSV. The rest will not be included. Is that correct?

[chinyeungli]

actually this was not fixed. The output CSV inventory BOM doesn't have the custom column key.