My Swift extensions

Here are my Swift extensions, as well as changes needed to make Lumberjack more Swift-friendly.
Just because something is listed as a `@property` doesn't mean a person has to `@synthesize` it.

I did it like this because it makes the following Swift code possible:

    Class aSwiftLogger: NSObject, DDLogger {
        // Using the loggerName variable to demonstrate this
        let loggerName = "Our Log name"
        
        // Also, variables can be defined like so:
        var loggerQueue: dispatch_queue_t {
            return dispatch_get_main_queue()
        }
    }

Still, if it is an issue, it can be reverted.