Move logging configuration to config file in local/

Currently, logging configuration is defined in bootstrap.php.  However, unlike email.php and database.php, which explicitly load local configuration from file in  local/Config/, the shipped bootstrap.php defines a number of default logs which cannot be easily changed locally; at least not without being overwritten when rolling out a new release (or causing git errors, in our deployment model).

Please consider moving the logging configuration to local/Config/logging.php (or similar) which can be included from botostrap.php and shipped as a default config similar to email.php.default.