Rename event-handlers to loggers, see #2979

* Rename config akka.event-handlers to akka.loggers
* Rename config akka.event-handler-startup-timeout to
  akka.logger-startup-timeout
* Rename JulEventHandler to JavaLogger
* Rename Slf4jEventHandler to Slf4jLogger
* Change all places in tests and docs
* Deprecation, old still works, but with warnings
* Migration guide
* Test for the deprecated event-handler config

akka-contrib/src/test/scala/akka/contrib/jul/JavaLoggerSpec.scala

@@ -0,0 +1,76 @@
+package akka.contrib.jul
+
+import com.typesafe.config.ConfigFactory
+import akka.actor.{ ActorSystem, Actor, ActorLogging, Props }
+import akka.testkit.AkkaSpec
+import java.util.logging
+import java.io.ByteArrayInputStream
+
+object JavaLoggerSpec {
+
+  val config = ConfigFactory.parseString("""
+    akka {
+      loglevel = INFO
+      loggers = ["akka.contrib.jul.JavaLogger"]
+    }""")
+
+  class LogProducer extends Actor with ActorLogging {
+    def receive = {
+      case e: Exception ⇒
+        log.error(e, e.getMessage)
+      case (s: String, x: Int) ⇒
+        log.info(s, x)
+    }
+  }
+}
+
+@org.junit.runner.RunWith(classOf[org.scalatest.junit.JUnitRunner])
+class JavaLoggerSpec extends AkkaSpec(JavaLoggerSpec.config) {
+
+  val logger = logging.Logger.getLogger("akka://JavaLoggerSpec/user/log")
+  logger.setUseParentHandlers(false) // turn off output of test LogRecords
+  logger.addHandler(new logging.Handler {
+    def publish(record: logging.LogRecord) {
+      testActor ! record
+    }
+
+    def flush() {}
+    def close() {}
+  })
+
+  val producer = system.actorOf(Props[JavaLoggerSpec.LogProducer], name = "log")
+
+  "JavaLogger" must {
+
+    "log error with stackTrace" in {
+      producer ! new RuntimeException("Simulated error")
+
+      val record = expectMsgType[logging.LogRecord]
+
+      record must not be (null)
+      record.getMillis must not be (0)
+      record.getThreadID must not be (0)
+      record.getLevel must be(logging.Level.SEVERE)
+      record.getMessage must be("Simulated error")
+      record.getThrown.isInstanceOf[RuntimeException] must be(true)
+      record.getSourceClassName must be(classOf[JavaLoggerSpec.LogProducer].getName)
+      record.getSourceMethodName must be(null)
+    }
+
+    "log info without stackTrace" in {
+      producer ! ("{} is the magic number", 3)
+
+      val record = expectMsgType[logging.LogRecord]
+
+      record must not be (null)
+      record.getMillis must not be (0)
+      record.getThreadID must not be (0)
+      record.getLevel must be(logging.Level.INFO)
+      record.getMessage must be("3 is the magic number")
+      record.getThrown must be(null)
+      record.getSourceClassName must be(classOf[JavaLoggerSpec.LogProducer].getName)
+      record.getSourceMethodName must be(null)
+    }
+  }
+
+}