New facility type in the basin box: underground permeable macadam basin

The basin box has been completed with a choice of specifying hydraulic conductivity k6, where k6=0 is the default and indicates the previous macadam basin with a tight bottom. The equation for calculating the exfiltration flow rate is given in the guide. The result for the new permeable bottom facility type is less required flow detention volume with increased permeability (k6 value).