Write a CSV to log changes

[sfkeller]

Write a CSV in addition to the audit.json that logs changes. This allows external applications to do evaluations and visualize progress.

Here is an example proposal of the CSV structure:

| project   | user       | feature               | type        |
|-----------|------------|-----------------------|-------------|
|<ProjektID>|<OSM-UserID>|<RefID from audit.json>|<Change-Type>|

See geometalab#2