[Nodeshot] Different database for network Statistic

[Gioacchino Mazzurco]

Hi!

The ntop.org developer have teached me that relational DB like mysql and 
postgre are suboptimal for store network statistics data, it is possible to 
use another database just for this kind of data?

Moreover for research purpose it would be very nice to have netflow support on 
nodeshot so we can plan better expansion for our networks :D