Remove version pins for google-apitools and oauth2client packages

This CL also adds (temporarily) the api client libraries for dataflow,
bigquery, and storage. We cannot publish these new packages because they
will break existing SDK releases.

----Release Notes----
Remove version pins for google-apitools and oauth2client packages.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=120143827

Author: silviulica

google/cloud/dataflow/internal/auth.py

@@ -140,7 +140,6 @@ def get_service_credentials():
 
       # The following code uses oauth2client >=2.0.0 functionality and if this
       # is not available due to import errors will use 1.5.2 functionality.
-      # TODO(silviuc): Remove the 1.5.2 when dependencies have been updated.
       try:
         from oauth2client.service_account import ServiceAccountCredentials
         return ServiceAccountCredentials.from_p12_keyfile(

google/cloud/dataflow/internal/clients/__init__.py

@@ -0,0 +1,10 @@
+"""Common imports for generated bigquery client library."""
+# pylint:disable=wildcard-import
+
+import pkgutil
+
+from apitools.base.py import *
+from google.cloud.dataflow.internal.clients.bigquery.bigquery_v2_client import *
+from google.cloud.dataflow.internal.clients.bigquery.bigquery_v2_messages import *
+
+__path__ = pkgutil.extend_path(__path__, __name__)