Logging improvements.

Log warnings and errors to a separate file.
Use log4js config files.
Rotate logs daily and clean up after 7 days.
Update log4js config and don't use /tmp.
Log, not logs.
Restore working production log4js.json
Stop writing output to obsolete log files.
No create /data/logs on startup
Add colors to logging.
Merge pull request #86 from jsha/log-rotation

Logging improvements