Advanced: ReserveProof: Add support for reserve proof

This change adds the ability to prove and check a reserve proof
to this existing "Prove/check" advanced menu. If the amount line has
a valid amount less than that of the current account index this input
will drive the logic for generating a reserve proof. Checking a reserve
proof is accomplished by validating the address and verifying that
signature.indexOf("ReserveProofV") === 0. The result displays the total
and spent amount of the proof.

js/TxUtils.js

@@ -61,6 +61,10 @@ function checkSignature(signature) {
         if ((signature.length - 12) % 88 != 0)
             return false;
         return check256(signature, signature.length);
+    } else if (signature.indexOf("ReserveProofV") === 0) {
+        if ((signature.length - 14) % 447 != 0)
+            return false;
+        return check256(signature, signature.length);
     }
     return false;
 }