Allow Zeronet python to use multiple CPU threads?

This is issue especially on zeronet proxies or when simply one is hosting many sites. You can see the zeronet is maxing out the CPU thread and leaves rest CPU threads unused.. I experienced this on all Linux distributions on which i tried to setup zeronet with [bigger number of zites](http://127.0.0.1:43110/1HMLvnRWViMnuvZc5LK4Dm86sZNcSH1jdh/?Topic:1553085871_1L4dZcDF2maSKHDy788yhxpYnBWnXadUtS/3212+zeronet+sites) and i think it may be lagging my Windows zeronet too. [Here is](http://127.0.0.1:43110/1TaLkFrMwvbNsooF4ioKAY9EuxTBTjipT/?Topic:1565037100_1L4dZcDF2maSKHDy788yhxpYnBWnXadUtS#comment_92_1EAD2zXkzgJf6M7xQ4jG5FHCxUTez9NJJ4) what largest zeronet proxy maintainer (d14n@) says about this.

Can ZeroNet be made to utilize more CPU threads?

https://stackoverflow.com/questions/4496680/python-threads-all-executing-on-a-single-core
https://stackoverflow.com/questions/203912/does-python-support-multiprocessor-multicore-programming
https://wiki.python.org/moin/GlobalInterpreterLock
https://docs.python.org/3/library/multiprocessing.html

No repository file, entry point, or test is named. Start with the linked Python threading, Global Interpreter Lock, and multiprocessing references, then inspect ZeroNet's current concurrency model; done would require a defined approach for using multiple CPU threads or processes and evidence that hosting many sites distributes CPU work safely.

索引モデルが issue の本文から書いたものです。