Introduce an 'initialize()' function that does the actual init
(session, cookies, config options) and can called separately from
the constructor __init__().
This allows, for example, to adjust config access inside a Job
before most of it already happened when calling 'extractor.find()'.
More precisely, it now splits the full 'filename' into 'name' and 'id'
instead of overwriting 'filename'. The format string stays the same as
before. Use '{name}.{extension}' to restore the old behavior.
before:
- filename: foobar
- id : 12345
now:
- filename: foobar-12345
- name : foobar
- id : 12345
