Merge pull request #2469 from prototech/ticket/12155

[ticket/12155] Construct post buttons using CSS.

* prototech/ticket/12155: (21 commits)
  [ticket/12155] Remove use of !important and move reddish color back to .button
  [ticket/12155] Reposition the button icons to the left side while we're at it.
  [ticket/12155] Get rid of line-height value causing alignment issues in FF.
  [ticket/12155] Get rid of the <span> where possible and fix buttons in Safari.
  [ticket/12155] Fix misplaced semicolon and ensure that value comparison works.
  [ticket/12155] Combine the post and topic/PM button icons into a single sprite
  [ticket/12155] Move icon class directly to <a> and use <span> consistently.
  [ticket/12155] Remove star hack from padding-right property of .button.
  [ticket/12155] Fix tabbing and put one selector per line if string is too long
  [ticket/12155] Make opacity transition faster and fix background image paths.
  [ticket/12155] Keep the selection method consistent with the one below it.
  [ticket/12155] Fade out the buttons when leaving the post.
  [ticket/12155] Display the buttons only when hovering the post.
  [ticket/12155] Make the buttons bigger on touch devices.
  [ticket/12155] Clean up icons.
  [ticket/12155] Remove unused font.
  [ticket/12155] Remove obsolete images.
  [ticket/12155] Use the new .button class as the basis for the post buttons.
  [ticket/12155] Move existing button style to a more generic class.
  [ticket/12155] Remove obsolete language images.
  ...