Improvement: max_time or max_cell to stop execution

[elmbeech]

so far, in setting.xml only max_time can be specified to stop the series.
it would be nice to have additionally a max_cell setting to stop the series, and execution would be stopped when either max_time or max_cell is reached.

<overall>
    <max_time units="min">14400</max_time>
    <max_cell units="agent">9000</max_cell>
    ....
</overall>