Decide how to handle opening book in webzebra

[panstromek]

We currently don't use the opening book at all, because it is very big (8.6MB) and I didn't want to slow the loading down too much and download a lot of stuff user won't necessarily use. There are few options:

1. Create a smaller book and always load it
   Booktool can be used for that I guess, but I don't really know how to use it. I'd have to dig a bit deeper to see what are the options.
   It's possible that this will bring a lot of value, even if the book is small, because if we cache just most common opening solutions, then the opening analysis will be much better and faster without too much CPU overhead

2. Load the book only if user requests it in some settings
   We can warn user that it's big and can take some time to load. This would provide more opening solutions, but provide no value by default.

3. Some combination of the above

   • small book with most common openings by default
   • large book if user requests it