README: Restructure and fix layout
README: Restructure and fix layout

- Fix headline formatting and update contents
- Restructure and remove sections that are now included in other repos
- Remove kernel quick start and update editable section
- Make formatting more consistent (e.g no line breaks in paragraphs)

Signed-off-by: Magnus Skjegstad <9f4ca770b638615ac5c3e0d2da16b77c80c2f2c6@skjegstad.com>

AnnikaH/IncludeOS,mnordsletten/IncludeOS,AnnikaH/IncludeOS,AndreasAakesson/IncludeOS,mnordsletten/IncludeOS,mnordsletten/IncludeOS,mnordsletten/IncludeOS,AnnikaH/IncludeOS,mnordsletten/IncludeOS,AnnikaH/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,AnnikaH/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,AndreasAakesson/IncludeOS,hioa-cs/IncludeOS,hioa-cs/IncludeOS,AndreasAakesson/IncludeOS,mnordsletten/IncludeOS