Fix for entity rendering X error

The pull request from thewierdnut renderes entities at a X position one
towards west. With this change entities are rendered at correct X
position (at least in my tests).
added id for Piston Extension

ID 34 is the head of a Piston and ID 36 is a technical block describing
all the stuff moved by the Piston. But Í have no idea about a good
color.