Split the dependency so that the encoders/decoders don't depend on arch.

arch/arch.h

@@ -0,0 +1,16 @@
+#pragma once
+
+class Encoder;
+class Decoder;
+class DecoderProto;
+class EncoderProto;
+class Config;
+
+namespace Arch
+{
+    std::unique_ptr<Decoder> createDecoder(Config& config);
+    std::unique_ptr<Decoder> createDecoder(const DecoderProto& config);
+
+    std::unique_ptr<Encoder> createEncoder(Config& config);
+    std::unique_ptr<Encoder> createEncoder(const EncoderProto& config);
+}