(WHO-900) Complain if no loggers are configured
(WHO-900) Complain if no loggers are configured

Throw an exception with a user-useful error message if no log4j loggers
are configured.

Without this change PCR is needlessly hard to troubleshoot because you
won't get useful log messages. Many of users users won't know how to
configure log4j so this ought to help.

Distelli/europa,Distelli/europa,Distelli/europa