This adds a new settings.LOGGING_TO_STDOUT flag. When set, log

entries will always be sent to stdout, alongside any configured log

file. This is needed for the Docker case, where a container is expected

to emit its log messages to stdout for capture.
We already had some fallback logging to stderr, in the event that we

couldn't write to a log file. That was intended for capture in the

Apache error_log. If LOGGING_TO_STDOUT is set, we no longer fall

back on this, since we can be sure we're already logging publicly.

Tested that logging was working correctly, with and without this

setting enabled.
Tested with DEBUG=True and DEBUG=False.