+act Add japi.Pair and japi.Predicate for streams

(cherry picked from commit 42ce37bb57884c7051d46a1e80b4a4ba4187adf4)

=act Add @SerialVersionUID to japi.Pair

(cherry picked from commit adb2c9bdc20effc84132daaf37e563fb430bf230)

akka-actor/src/main/scala/akka/japi/JavaAPI.scala

@@ -45,6 +45,19 @@ trait Effect {
   def apply(): Unit
 }
 
+/**
+ * Java API: Defines a criteria and determines whether the parameter meets this criteria.
+ */
+trait Predicate[T] {
+  def test(param: T): Boolean
+}
+
+/**
+ * Java API: Represents a tuple of two elements.
+ */
+@SerialVersionUID(1L)
+case class Pair[A, B](first: A, second: B)
+
 /**
  * A constructor/factory, takes no parameters but creates a new value of type T every call.
  */