Document DB (in)compatibility

[roman-khimov]

Is your feature request related to a problem? Please describe.

I'm always frustrated when @532910 is frustrated. As a professional system administrator he can't remember which options affect DB compatibility between nodes. No wonder, resynchronizations happen once in several months, we need to resynchronize at least bi-weekly for these things to not get forgotten.

Describe the solution you'd like

Add a section to docs/node-configuration.md that describes DB compatibility between different nodes. Document all known arch/config settings for Level and Bolt that can affect it. We have these things mentioned for individual options, but it's not easy to get an answer on "I want to copy the DB, will it work?" question.