[RFE] Allow Severity Level for different apisonator component logs to be configured

[mpguerra]

Currently there is no way to define a severity level for logging apisonator events.

For customers with large numbers of requests, they can find that they are using a lot of disk storage for daily logs at the current log level.

• For backend-listener
  • request logs
  • server logs
• For backend-worker
  • Can currently send logs to /dev/null by setting the CONFIG_WORKERS_LOG_FILE but this means that no logs are sent.
  • INFO events are currently logged for every report job.
• Other components?

It would be very useful to be able to set the log level with a variable, e.g rails_log_level

INFO, WARNING and ERROR severity levels should be enough for most customers, although we may want to think about adding a DEBUG level also depending on the component.

[mpguerra]

This JIRA deals with documenting this across the product: https://issues.jboss.org/browse/THREESCALE-862