Clean up and organize README

[joukos]

The main README is too long. There's old but valid documentation way too far to be comfortably scrolled to because of meandering hit-and-run updates and not having the time to keep the docs concise and updated.

Some stuff to do:

• [ ] VNC feature should be included in the command line instructions
  • [ ] VNC instructions could be a bit more thorough, too
• [ ] Images are nice to have, but they could be clickable thumbnails in tables (or something) so they won't take most of the space
• [ ] Clean up, fix historical remarks etc.

This would be easiest for me to do, but since it's so hard to get a proper moment to do it, I've created this issue to nag me. And if I never get around to it, maybe someone else with a knack for documentation will :)

[chi-lambda]

Github has a wiki feature. Would that be a better format?

[joukos]

In some other old project I used the Wiki, but the problem is that no one looks there :) If there's a whole library of information, it might be useful, but I think in this case it would be more effective to clean up the main README.