Use PSR LoggerInterface instead of Ruckusing_Util_Logger.

[herregroen]

The Ruckusing_Util_Logger is not PSR compatible ( see https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-3-logger-interface.md ). It's log method should accept a log level as the first argument and the message as the second argument.

Because the Ruckusing_Util_Logger is not PSR compatible it's impossible to reuse existing loggers that will in all likelihood be compatible with that standard.

All methods that accept a Ruckusing_Util_Logger should also be typehinted with LoggerInterface instead so that projects may more easily reuse existing loggers.