Review cleanup

- Add constructors for ConnIDKey, remove BuildConnIDKey()
- Rename protocol stats classes and move to implementation file
- Rename "num" field of protocol stats to "active"
- Explicitly delete copy operations for SessionKey
- Change argument for ProtocolStats methods to const-reference
- Make key validity methods in Session not be virtual
- Rename Session::ClearKey and Session::IsKeyValid

src/Conn.h

@@ -116,8 +116,6 @@ public:
 	const detail::ConnIDKey& Key() const	{ return key; }
 	detail::SessionKey SessionKey(bool copy) const override
 		{ return detail::SessionKey{&key, sizeof(key), copy}; }
-	void ClearKey() override			{ key_valid = false; }
-	bool IsKeyValid() const	override	{ return key_valid; }
 
 	const IPAddr& OrigAddr() const		{ return orig_addr; }
 	const IPAddr& RespAddr() const		{ return resp_addr; }
@@ -271,7 +269,6 @@ protected:
 	std::shared_ptr<EncapsulationStack> encapsulation; // tunnels
 
 	detail::ConnIDKey key;
-	bool key_valid;
 
 	unsigned int skip:1;
 	unsigned int weird:1;