[ticket/12155] CSS-ing of the mini post buttons

Created a css version of the mini post buttons with the use of language vars
and no fixed width of height.

PHPBB3-12155
[ticket/12155] Remove obsolete language images.

PHPBB3-12155
[ticket/12155] Move existing button style to a more generic class.

PHPBB3-12155
[ticket/12155] Use the new .button class as the basis for the post buttons.

PHPBB3-12155
[ticket/12155] Remove obsolete images.

PHPBB3-12155
[ticket/12155] Remove unused font.

PHPBB3-12155
[ticket/12155] Clean up icons.

PHPBB3-12155
[ticket/12155] Make the buttons bigger on touch devices.

PHPBB3-12155
[ticket/12155] Display the buttons only when hovering the post.

PHPBB3-12155
[ticket/12155] Fade out the buttons when leaving the post.

PHPBB3-12155
[ticket/12155] Keep the selection method consistent with the one below it.

PHPBB3-12155
[ticket/12155] Make opacity transition faster and fix background image paths.

PHPBB3-12155
[ticket/12155] Fix tabbing and put one selector per line if string is too long

PHPBB3-12155
[ticket/12155] Remove star hack from padding-right property of .button.

This was in place for IE7 due to the use of :after for inserting the button
icon. IE7 does not support :after, so the hack removed the extra padding that
made room for the icon. We no longer use :after for the icon, so this is no
longer an issue... not to mention that IE7 is no longer supported.

PHPBB3-12155
[ticket/12155] Move icon class directly to <a> and use <span> consistently.

PHPBB3-12155
[ticket/12155] Combine the post and topic/PM button icons into a single sprite

PHPBB3-12155
[ticket/12155] Fix misplaced semicolon and ensure that value comparison works.

PHPBB3-12155
[ticket/12155] Get rid of the <span> where possible and fix buttons in Safari.

PHPBB3-12155
[ticket/12155] Get rid of line-height value causing alignment issues in FF.

PHPBB3-12155
[ticket/12155] Reposition the button icons to the left side while we're at it.

PHPBB3-12155