Allow modifying log levels of individual Play classes and packages

The current logging setup is an all or nothing approach where to change a log level for one class means you must change it for all classes, which is incredibly frustrating

Someone with Scala experience please check whether I am creating too many loggers. In Java I create them as static variables. In Scala there are classes, objects, traits, singletons, etc. that all have loggers. With the objects and singletons I believe I am only creating one total and not one per object instantiation. I have no idea with the traits though.
Yes, the class of the object ends with $. I think `classOf[MyClass]` is going to be the simplest. That avoids the logs showing `MyClass$`. For objects without a companion class I think `this.getClass` is fine. It looks like logback will allow that to be configured without the $, I guess treating it as an inner class.