The valueButton element specifies a button for each step in the tariff
<valueButton id="4" duration="60" amount="100" durationText="1h00" amountText="1.00"/>
attributes
| ID: | 1 to the number of buttons needed |
| duration: | The duration for this tariff step |
| Amount: | The amount for this step |
| DurationText: | The duration text to display |
| AmountText: | The amount text to display |
