Javadoc spruce-up

[ddimtirov]

• [x] Fix style to look more normal
• [x] Fix not to double the Jetbrains annotations
• [x] Add entry-point markers
• [x] Syntax-colorize sample code
• [x] Add the current API version
• [x] tweak sizes - only html in pixels, everything else in rems
• [x] tweak media
  • [x] hidpi
  • [x] lodpi
  • [x] phone
  • [x] print