Added formulas for ntopng and ndpi

Dear all, please find enclosed the formulas for two open source tools ntop develops:
- nDPI: SDK for deep-packet inspection
- ntopng: web-based traffic monitoring application.

Thanks Luca Deri
Can this test be modified to do something more substantial then e.g. `--version` or `--help`? See `cmake.rb` for an example of a formula with a good test. Thanks!