Fix account balance calculation on deposit

[monicanagent]

Currently an account's balance is stored using direct data from the blockchain when a deposit is detected. However, a fee is applied when the amount is transferred which should reduce the available balance by the fee. In other words:

available account balance = detected deposit amount - miner fee

Additionally, the address associated with the account does not appear to be currently emptied. For example: https://live.blockcypher.com/btc-testnet/address/mtqmdZFqjqrPk1TRwU8S3WWazfYT6mNYFb/

Verify that the transfer amount calculation is being correctly done.

[monicanagent]

Fixed with revision 87 (b85396a).