DataMod (new): create a CSV file with statistical data
DataMod: more data, more options
DataMod: make flow filter optional (connection filter remains mandatory)
code cleanup
DataMod: Add gnuplot options
DataMod: prevent DIV zero
DataMod: bugfixes
DataMod: account for sequence number overflow
DataMod: use U.percent(...) where possible
DataMod: fix serial number comparison
DataMod: add possibility for max_sequence == 0