wallet/transferAmount - Transfer an amount to another wallet.

Method parameters:
id - The ID of the wallet to transfer an amount from.
to_id - The ID of the wallet to transfer an amount to.
amount - The amount to transfer.
description - The description of the transaction.

Returns a JSON document of the following format:
<boolean> - Always true.

Expected errors:
WALLET_NOT_FOUND - A wallet with the ID to transfer the amount from doesn't exist.
TO_WALLET_NOT_FOUND - A wallet with the ID to transfer the amount to doesn't exist.
TO_WALLET_SAME - The wallet to transfer from and the wallet to transfer to are the same.
ENTER_AMOUNT - The amount is zero.