Added javadocs for Function and Procedure

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

@@ -1,9 +1,16 @@
 package se.scalablesolutions.akka.util
 
+/** A Function interface
+ * Used to create first-class-functions is Java (sort of)
+ * Java API
+ */
 trait Function[T,R] {
   def apply(param: T): R
 }
 
+/** A Procedure is like a Function, but it doesn't produce a return value
+ * Java API
+ */
 trait Procedure[T] {
   def apply(param: T): Unit
 }