- Related to LBCORE-32

  added support for passing the configuration file as a system property.
  The system property name is "logback.configurationFile". Values can be 
  of type URL, a file, or a resource name.

  I am guessing that this modification should satisfy the requirements
  for most users who voted on this issue. I am not too keen on adding
  other config directives as system properties as suggested by M. Fowles.