Log pile graphical upgrade

WingedRayeth on the forums asked for [logpiles to graphically look like ingot piles](http://terrafirmacraft.com/f/topic/5408-make-pit-kiln-log-placement-work-for-log-piles/). I thought it sounded like a nice upgrade. So here's code to do exactly that, without changing in any way how logpiles are interacted with. 
![Sample screenshot](https://cloud.githubusercontent.com/assets/1906649/2755830/31e15548-c96e-11e3-8497-69d1a8dca302.png)