New design for show more/less buttons

All expander buttons have this appearance in fronts and trail blocks:

![screen shot 2013-10-03 at 13 17 32](https://f.cloud.github.com/assets/85783/1261165/073ba1c6-2c26-11e3-8231-92860ada14c3.PNG)

![ ](http://s2.developerslife.ru/public/images/gifs/30f8ea26-bc57-41d4-ab74-35894c848114.gif)