Make Local Onion Persistent Between Restarts

Unless mistaken, in `TorManager.py`, method `addOnion`, the private keys are never saved anywhere and never re-used preventing the onion addresses from being persistent between ZeroNet restarts.

Since libzeronet's primary concern is performance for resilient super-peers (eligible for eventual inclusion in the bootstrapable peer list in `Config.py`), this issue is libzeronet-related and a solution for it might be included in my libzeronet-backed port of the Python stack.

Start in TorManager.py at addOnion and inspect how private keys and onion addresses are currently handled across a restart. Review Config.py for the bootstrapable peer context and determine a suitable persistence path from the existing project structure. Done means the private key is saved, reused after a ZeroNet restart, and the onion address remains unchanged.

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