Network Layer 7 rework (Packet handling)

* Move networkcode to a dedicated directory
* Rename clientserver.h to network/networkprotocol.h (Better name) and sanitize some includes
* Create object NetworkPacket
  * It stores command (opcode) and data separated
  * It also stores peer_id
  * Data reading can be done by using a streaming interface
* Change packet routing analysis
  * Remove old conditional analysis
  * Now uses function pointed analysis and add connection state ({Client,Server}::handlers)
  * Connection state permit to categorize condition to handle before analyze packets
  * Create a handler for depreciated messages, instead of duplicating code

src/filecache.cpp

@@ -20,7 +20,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "filecache.h"
 
-#include "clientserver.h"
+#include "network/networkprotocol.h"
 #include "log.h"
 #include "filesys.h"
 #include <string>