=pro #23931 define automatic module names explicitly (#23960)

* =pro #23931 define automatic module names explicitly (otherwise would be akkaactor_2.12) etc

Read:
- http://blog.joda.org/2017/04/java-se-9-jpms-module-naming.html
- http://mail.openjdk.java.net/pipermail/jpms-spec-experts/2017-February/000582.html
- http://blog.joda.org/2017/05/java-se-9-jpms-automatic-modules.html

for rationale

* Update build.sbt

* Update build.sbt

project/AutomaticModuleName.scala

@@ -0,0 +1,23 @@
+/**
+ * Copyright (C) 2016-2017 Lightbend Inc. <http://www.lightbend.com>
+ */
+package akka
+
+import sbt.{Def, _}
+import sbt.Keys._
+
+/**
+ * Helper to set Automatic-Module-Name in projects.
+ *
+ * !! DO NOT BE TEMPTED INTO AUTOMATICALLY DERIVING THE NAMES FROM PROJECT NAMES !!
+ *
+ * The names carry a lot of implications and DO NOT have to always align 1:1 with the group ids or package names,
+ * though there should be of course a strong relationship between them.
+ */
+object AutomaticModuleName  {
+  private val AutomaticModuleName = "Automatic-Module-Name"
+
+  def settings(name: String): Seq[Def.Setting[Task[Seq[PackageOption]]]] = Seq(
+    packageOptions in (Compile, packageBin) += Package.ManifestAttributes(AutomaticModuleName → name)
+  )
+}