Support for review with ELF OpenGo

[renanpablocruz]

Facebook released an AlphaGoZero reimplementation which seems to be quite strong. It would be nice having support for it.
https://facebook.ai/developers/tools/elf-opengo
https://ai.facebook.com/blog/open-sourcing-new-elf-opengo-bot-and-go-research/

[alreadydone]

ELF models can be easily converted into Leela Zero format, which is how the majority people use the ELF models (with Lizzie, or GRP etc.). The ELF engine finally has a Windows version, but it's not optimized for lower playouts and probably slower, so it's preferable to continue to use LZ and not worth it to support the ELF engine. All that said, it's up to @pnprog to decide.

[wonderingabout]

i would always use the native engine whenever i can @renanpablocruz

plus leela zero is known to have many blindspot issue both at low and high playouts 👍

[pnprog]

This is worth a try at least, maybe some interesting features could be provided using the original engine.

I will have a try, but first I need to finish support for PhoenixGo.