libweave: Add unittests for dbus_conversion.h

Added DBusConversionTest.DictionaryToDBusVariantDictionary test.
Others moved from schema_utils_unittests.cc.
Added serialization of "[[],[]]" as vector<Any>.

BUG=brillo:1245
TEST='FEATURES=test emerge-gizmo buffet'

Change-Id: Ib93a612d5d8dc45615912325b4f3c1d3877af976
Reviewed-on: https://chromium-review.googlesource.com/287845
Trybot-Ready: Vitaly Buka <vitalybuka@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
diff --git a/buffet/buffet.gyp b/buffet/buffet.gyp
index ee41d23..7cd6db0 100644
--- a/buffet/buffet.gyp
+++ b/buffet/buffet.gyp
@@ -195,6 +195,7 @@
             '../libweave/src/commands/command_queue_unittest.cc',
             '../libweave/src/commands/dbus_command_dispatcher_unittest.cc',
             '../libweave/src/commands/dbus_command_proxy_unittest.cc',
+            '../libweave/src/commands/dbus_conversion_unittest.cc',
             '../libweave/src/commands/object_schema_unittest.cc',
             '../libweave/src/commands/schema_utils_unittest.cc',
             '../libweave/src/commands/unittest_utils.cc',