Implement BCSTransfer in REST API

[kPatch]

/// <summary>
/// TODO: Complete
/// </summary>
/// <param name="callback"></param>
/// <param name="sender"></param>
/// <param name="recipient"></param>
/// <param name="amount"></param>
/// <returns></returns>
public IEnumerator BCSTransfer(Action<string> callback, Account sender, string recipient, int amount)
{
    Utilities.BCS.AccountAddress recipientArg = new Utilities.BCS.AccountAddress(recipient);
    U64 amountArg = new U64((ulong)amount);

    Utilities.BCS.AccountAddress accountAddress = new Utilities.BCS.AccountAddress("0x01");
    ModuleId moduleId = new ModuleId(accountAddress, "coin");

    ISerializable[] transactionArguments =
    {
        recipientArg,
        amountArg
    };

    StructTag structTag = new StructTag(accountAddress, "aptos_coin", "AptosCoin", new ISerializableTag[0]);
    ISerializableTag[] typeTags = new ISerializableTag[] { structTag };

    EntryFunction entryFunction = new EntryFunction(
        moduleId, 
        "transfer",
        new TagSequence(typeTags), 
        new Utilities.BCS.Sequence(transactionArguments)
    );

    TransactionPayload txnPayload = new TransactionPayload();

    yield return null;
}