Piston bastion fix

A fix for the piston bastion issues noted at http://www.reddit.com/r/Civcraft/comments/28j5oq/bastion_fields_and_pistons/ . Re-adds the ability for pistons to push 

*Please note that due to citadel API issues (wrong version?) I can't compile Bastion mod at all.* Will need to get another dev to review & compile (good idea anyway).