Add opportunity to setup debug antilog levels

[AAkira]

Napier is originally designed to be used with your own customization of AntiLog. However, Napier provided a DebugAntilog for easy debugging on each platform. Therefore, we basically want you to customize Antilog on your own. However, we understand your desire to use DebugAntilog.

How about inheriting DebugAntilog like this?

• Added the open modifier on DebugAntilog

actual open class DebugAntilog actual constructor(private val defaultTag: String) : Antilog() {
}

• New

class MyDebugAntilog(defaultTag: String) : DebugAntilog(defaultTag) {
    override fun isEnable(priority: LogLevel, tag: String?): Boolean = priority > LogLevel.INFO
}