Implement structured logging

[pombredanne]

We need to have multiple levels of logging, preferably stored in the DB:

1. at the importer level, we want to know when we ran an import with a summary of what was imported, a date
2. this could also have a list of errors in a separate log (table?)
3. at the improver level, we should update a per-record log that briefly tells when which improver ran that modified data

[sify21]

Is there a way to set global logging level?

[pombredanne]

@sify21 re:

Is there a way to set global logging level?

Not at the moment. The story on logging is in flux for now. Eventually we want to have logging going to the DB as described in this issue and I reckon that logging is way too verbose at this stage.
If you feel like lending a hand here that would be great!