Filter buttons are now of fixed width.

So far, the '-' buttons were slightly less broad.
Removed 'neutral' filter buttons.

Function was not always clear to users.
Added border around references link.
Set minimum width of page.
Changed fonts to be closer to the design.
Changed start of all filter names to upper case.
Added color to the checkmarks in the methods.
Added unicode 'crossmark' instead of 'x'.
Minor fixes.
Added downward arrow to the filter section.
Added highlighting for the number of matches.