Allow pistons to push within same-group bastion field

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 unreinforced blocks within a bastion field if they are either:

* Group reinforced to the same group as the bastion.
* Privately reinforced, and the owner is a member of the bastion group.

*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).