buffet: Moved D-Bus definitions to XML/Code generator

Moved D-Bus interface definitions for buffet to XML files and using
the code generator to produce adaptors/proxies. Switched over the
implementations of objects to using the generated adaptors and using
the generated proxies in buffet_client.

Some more work on proxy generator is required to switch over the
usage of Command/CommandListener in libbuffet to using the generated
proxies, since the generator does not support D-Bus properties or
Object Manager yet.

BUG=chromium:435591
TEST=FEATURES=test emerge-link buffet

Change-Id: If010ee70b356d146e4a35a7301a753c9c54377f5
Reviewed-on: https://chromium-review.googlesource.com/231350
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/commands/dbus_command_dispatcher_unittest.cc b/buffet/commands/dbus_command_dispatcher_unittest.cc
index ed272a1..8033390 100644
--- a/buffet/commands/dbus_command_dispatcher_unittest.cc
+++ b/buffet/commands/dbus_command_dispatcher_unittest.cc
@@ -116,11 +116,11 @@
   }
 
   void FinishCommand(DBusCommandProxy* proxy) {
-    proxy->HandleDone();
+    proxy->Done();
   }
 
   void SetProgress(DBusCommandProxy* proxy, int progress) {
-    proxy->HandleSetProgress(nullptr, progress);
+    proxy->SetProgress(nullptr, progress);
   }