Refactor docs

[hunicus]

This PR is a redo of #1036, which was closed since it got out-of-date with the Liquid and Liquid testnet updates.

Benefits:

• Move all endpoint data to one file to make updating and adding new endpoints less of a pain
• Allow for descriptions that vary by network, which is a need I encountered when auditing docs for accuracy

Todo:

• Audit docs for accuracy (this new structure makes that much easier)

I really wanted to get rid of a lot of the 'wrapper' functions, empty code sample items, and other things but those fixes weren't obvious to me so I leave them for future PRs. I think these changes at least make the docs more manageable for all involved and will allow me to get on with fixing higher-priority issues like accuracy, layout, etc.

[wiz]

Tested ACK @ v2.4.0-dev [43e6045]
Everything seems to work exactly as is it did before, except the code is much cleaner :)