i2psnark: Stub out BEP 52 message numbers

Hide BEP 48 padding directory from UI
Check for and reject BEP 52 info multihashes for now
Use cached fai.isDirectory for efficiency
Use storage.getFileCount() instead of meta.getFiles() to prep for padding files
Add notes for padding file TODOs

apps/i2psnark/java/src/org/klomp/snark/Message.java

@@ -49,6 +49,9 @@ class Message
   final static byte REJECT       = 16;  // Fast (BEP 6)
   final static byte ALLOWED_FAST = 17;  // Fast (BEP 6)
   final static byte EXTENSION    = 20;  // BEP 10
+  final static byte HASH_REQUEST = 21;  // BEP 52
+  final static byte HASHES       = 22;  // BEP 52
+  final static byte HASH_REJECT  = 23;  // BEP 52
   
   // Not all fields are used for every message.
   // KEEP_ALIVE doesn't have a real wire representation
@@ -278,6 +281,13 @@ class Message
         return "REJECT(" + piece + ',' + begin + ',' + length + ')';
       case ALLOWED_FAST:
         return "ALLOWED_FAST(" + piece + ')';
+      // BEP 52 below here
+      case HASH_REQUEST:
+        return "HASH_REQUEST";
+      case HASHES:
+        return "HASHES";
+      case HASH_REJECT:
+        return "HASH_REJECT";
       default:
         return "UNKNOWN (" + type + ')';
       }