Add python:3 action support.

Update tests to work in both Python 2 and Python 3.
Rename pythonaction to python3action for container image name for clarity.
Add tests for python:2 and python:3.
Add image names for all the actions. Rename javaaction to java8action for consistency.
diff --git a/core/javaAction/build.gradle b/core/javaAction/build.gradle
index f04bf97..8688fd7 100644
--- a/core/javaAction/build.gradle
+++ b/core/javaAction/build.gradle
@@ -1,2 +1,2 @@
-ext.dockerImageName = 'javaaction'
+ext.dockerImageName = 'java8action'
 apply from: '../../gradle/docker.gradle'
diff --git a/settings.gradle b/settings.gradle
index ed84a46..1955feb 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -6,6 +6,7 @@
 include 'core:nodejs6Action'
 include 'core:actionProxy'
 include 'core:pythonAction'
+include 'core:python2Action'
 include 'core:swift3Action'
 include 'core:javaAction'
 
diff --git a/tests/build.gradle b/tests/build.gradle
index f9e95d9..32275c2 100644
--- a/tests/build.gradle
+++ b/tests/build.gradle
@@ -27,6 +27,7 @@
     ':core:nodejs6Action:distDocker',
     ':core:actionProxy:distDocker',
     ':core:pythonAction:distDocker',
+    ':core:python2Action:distDocker',
     ':core:javaAction:distDocker',
     ':core:swift3Action:distDocker',
     ':sdk:docker:distDocker',
diff --git a/tests/src/test/scala/actionContainers/JavaActionContainerTests.scala b/tests/src/test/scala/actionContainers/JavaActionContainerTests.scala
index 1eba705..555c9c5 100644
--- a/tests/src/test/scala/actionContainers/JavaActionContainerTests.scala
+++ b/tests/src/test/scala/actionContainers/JavaActionContainerTests.scala
@@ -31,8 +31,8 @@
 @RunWith(classOf[JUnitRunner])
 class JavaActionContainerTests extends FlatSpec with Matchers with WskActorSystem with ActionProxyContainerTestUtils {
 
-    // Helpers specific to javaaction
-    def withJavaContainer(code: ActionContainer => Unit, env: Map[String, String] = Map.empty) = withContainer("javaaction", env)(code)
+    // Helpers specific to java actions
+    def withJavaContainer(code: ActionContainer => Unit, env: Map[String, String] = Map.empty) = withContainer("java8action", env)(code)
 
     override def initPayload(mainClass: String, jar64: String) = JsObject(
         "value" -> JsObject(