Add corresponding Invoice Balance in Customer Statements

//info: CDU-949

In most cases, statements are generated based on records such as INV, Credit Memos, and Payments.
The system counts the credits and overpayments on top and displays the results in the Balance field.

Solution:
We have created another column for showing the balance for each row.

      <tr>
	<td colspan="3">${line.datecol}</td>
	<td colspan="12">${line.description}</td>
	<td align="right" colspan="3">${line.charge}</td>
	<td align="right" colspan="4">${line.payment}</td>
        <td align="right" colspan="6">${line.amountremaining}</td>
	<td align="right" colspan="4">${line.balance}</td>
     </tr>