fix CSS errors

- we had some illegal syntax, causing some formats to be ignored
- especially the up-to-now ignored bold paragraph titles don't
  look good; thus I'll revert them to non-bold
- the CSS selector for the footnote number also selected
  hypelinks within the footnote text. We need to introduce
  a specific class for the footnote number to resolve this issue
- the table cells included spurious margins, inherited from
  the regular text paragaph setting
switch the credits to new table syntax
update contributors
small fixes here and there