Indent all the things with 4 spaces

- Add vim modelines to maybe enforce this
- Indentation has been skipped for the occasional HTML element with only
  one child
- Also change other small things arising from scanning the entire code
  base
Indent a few extra missed things
Indent config.php.EXAMPLE and CSS too (fixes #16)

- since CSS size matters, also single-line CSS declarations with a
  single property
Polish code spacing further

might as well do it all at once