Refactoring documentation tree

[XMRZombie]

Lots of documentations everywhere it becomes an unclear one

[boldsuck]

You mean the 'nav' menu?
I took most of it from Haveno-docs.

I can also make everything about the Haveno-UI, as with Payments, into a drop-down menu. Maybe Development & The Project, too.

EDIT:
Drop-down doesn't work as I want. What about tabs?
https://squidfunk.github.io/mkdocs-material/setup/setting-up-navigation/#navigation-tabs

I have already combined some things into one file. Backup and restore were previously 2 files. Account limits & Account signing, too. I would also like to summarize Getting Started & Getting Started 2.

I want to adjust all the trade limits for Haveno .15. And go through everything again, looking at typos, making all headings the same size, setting some line brakes, some formatting nicer, etc.
Automatically light, dark settings from OS.
Haveno-reto renaming in RetoSwap.

The most important thing for me was to first finish the docu that the app links to.
@woodser has already adjusted links. I think there are still one or two wrong.