[ErrorLog] Add expand_newlines option to the error_log handler

[Amoifr]

Per request in #580: exposes the $expandNewlines constructor argument of Monolog's ErrorLogHandler as a new expand_newlines boolean config option (defaults to false, preserving current behavior).

monolog:
    handlers:
        main:
            type:            error_log
            message_type:    0
            expand_newlines: true

Fix #580

[GromNaN]

Thank you @Amoifr.