Save attack stats into the internal database

[yuchdev]

Colleagues, I was checking out open problems, and I found at least 3 of them may require the common underlying functionality: porthole-ascend-cinnamon/mhddos_proxy#191, porthole-ascend-cinnamon/mhddos_proxy#105, porthole-ascend-cinnamon/mhddos_proxy#107 require dynamic analysis of the ongoing attack stats, or an access to the historical data about attacks.

It may lead to the conclusion we need to save the ongoing attack stats, with all the required data, like timestamps, performance tickers, selected proxies, it could makes sense to give one particular attack some sort of ID, etc etc.

As an initial step, I suggest using the SQLite database, as a part of the Python standard library, and offering sufficient tools for queries and basic analytics.