Minor bugs in datageneration.py

[akemaristide]

Thanks for these files. It really streamlines the data extraction and processing.

I found these three possible bugs:

https://github.com/nds-group/DUNE/blob/master/data_generation/src/datageneration.py#L23
Double repetition of "min": 'Flow IAT Min': 'min', 'Flow IAT Max': 'min'
--> 'Flow IAT Max': 'max'

https://github.com/nds-group/DUNE/blob/master/data_generation/src/datageneration.py#L311
packet_data.loc[packet_data['pkt_number'] >= n, feature] * 10e9).round(9)
--> 10e9 = 1e10, not 1e9 as possibly intended.

https://github.com/nds-group/DUNE/blob/master/data_generation/src/datageneration.py#L282
--> packet_data['flow_iat'] = packet_data.groupby('Flow ID')['frame.time_relative'].diff().fillna(0)
Computing the IAT like this seems to imply the minimum IAT is always zero. It might be better to exclude the first 0.