Factored Conformance and Benchmark test messages into shared test schema. (#1971)

* Factored Conformance test messages into shared test schema.

* Updated benchmarks to use new proto3 message locations.

* Fixed include path.

* Conformance: fixed include of Python test messages.

* Make maven in Rakefile use --batch-mode.

* Revert changes to benchmarks.

On second thought I think a separate schema for
CPU benchmarking makes sense.

* Try regenerating C# protos for new test protos.

* Removed benchmark messages from test proto.

* Added Jon Skeet's fixes for C#.

* Removed duplicate/old test messages C# file.

* C# fixes for test schema move.

* Fixed C# to use the correct TestAllTypes message.

* Fixes for Objective C test schema move.

* Added missing EXTRA_DIST file.
diff --git a/conformance/conformance_python.py b/conformance/conformance_python.py
index 2f4a781..7ace9b1 100755
--- a/conformance/conformance_python.py
+++ b/conformance/conformance_python.py
@@ -38,8 +38,9 @@
 import struct
 import sys
 import os
-from google.protobuf import message
 from google.protobuf import json_format
+from google.protobuf import message
+from google.protobuf import test_messages_proto3_pb2
 import conformance_pb2
 
 sys.stdout = os.fdopen(sys.stdout.fileno(), 'wb', 0)
@@ -52,9 +53,9 @@
   pass
 
 def do_test(request):
-  test_message = conformance_pb2.TestAllTypes()
+  test_message = test_messages_proto3_pb2.TestAllTypes()
   response = conformance_pb2.ConformanceResponse()
-  test_message = conformance_pb2.TestAllTypes()
+  test_message = test_messages_proto3_pb2.TestAllTypes()
 
   try:
     if request.WhichOneof('payload') == 'protobuf_payload':