ODK and Shared Libraries

In this code drop we introduce the ODK dependency. The reference
implementation has been updated to make use of the ODK and the related
tests have been included.

In addition, we have included an example of how a shared libraries can
be created. This will allow make it easier to test and verify different
implementations of the API.

Most other changes introduce by this code drop were made to clean-up the
reference implementation and limit dependencies.

api/license_whitebox_get_secret_string_test.cc

@@ -48,12 +48,14 @@ class LicenseWhiteboxGetSecretStringTest : public LicenseWhiteboxTestBase {
     License license;
     builder.Build(*public_key_, &license);
 
-    ASSERT_EQ(WB_License_ProcessLicenseResponse(
-                  whitebox_, license.message.data(), license.message.size(),
-                  license.signature.data(), license.signature.size(),
-                  license.session_key.data(), license.session_key.size(),
-                  license.request.data(), license.request.size()),
-              WB_RESULT_OK);
+    ASSERT_EQ(
+        WB_License_ProcessLicenseResponse(
+            whitebox_, license.core_message.data(), license.core_message.size(),
+            license.message.data(), license.message.size(),
+            license.signature.data(), license.signature.size(),
+            license.session_key.data(), license.session_key.size(),
+            license.request.data(), license.request.size()),
+        WB_RESULT_OK);
   }
 
   // We need two special keys for this test, one that will be used for a