Marked FailureDetectorLoader as akka private

- also added scaladoc

akka-remote/src/main/scala/akka/remote/FailureDetectorRegistry.scala

@@ -47,8 +47,21 @@ trait FailureDetectorRegistry[A] {
   def reset(): Unit
 }
 
-object FailureDetectorLoader {
+/**
+ * Utility class to create [[FailureDetector]] instances reflectively.
+ */
+private[akka] object FailureDetectorLoader {
 
+  /**
+   * Loads and instantiates a given [[FailureDetector]] implementation. The class to be loaded must have a constructor
+   * that accepts a [[com.typesafe.config.Config]] and an [[EventStream]] parameter. Will throw ConfigurationException
+   * if the implementation cannot be loaded.
+   *
+   * @param fqcn Fully qualified class name of the implementation to be loaded.
+   * @param config Configuration that will be passed to the implementation
+   * @param system ActorSystem to be used for loading the implementation
+   * @return A configured instance of the given [[FailureDetector]] implementation
+   */
   def load(fqcn: String, config: Config, system: ActorSystem): FailureDetector = {
     system.asInstanceOf[ExtendedActorSystem].dynamicAccess.createInstanceFor[FailureDetector](
       fqcn, List(
@@ -59,6 +72,16 @@ object FailureDetectorLoader {
       }).get
   }
 
+  /**
+   * Loads and instantiates a given [[FailureDetector]] implementation. The class to be loaded must have a constructor
+   * that accepts a [[com.typesafe.config.Config]] and an [[EventStream]] parameter. Will throw ConfigurationException
+   * if the implementation cannot be loaded. Use [[FailureDetectorLoader#load]] if no implicit [[ActorContext]] is
+   * available.
+   *
+   * @param fqcn Fully qualified class name of the implementation to be loaded.
+   * @param config Configuration that will be passed to the implementation
+   * @return
+   */
   def apply(fqcn: String, config: Config)(implicit ctx: ActorContext) = load(fqcn, config, ctx.system)
 
 }