[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
Merge pull request #5 from prototech/ticket/12155

Ticket/12155