A field trial for the automatically named logger.

Can be enabled with -Dorg.slf4j.LoggerFactory.autoNamedLoggerFieldTrial=true.

Prints an error (and stacktrace) to stderr when a mismatch between custom and automatic logger names is detected.
Remove stack trace from the field trial mismatch message.
Merge pull request #92 from adorokhine/getlogger_field_study

A field trial for the automatically named logger.