Build Helper - Change how to select the center

Hello. So this idea is to make the build helper select a block exactly like how the create docking has you select where the core will go. The reason I suggest this is because many times I want to create a shape over an area that already has a docked entity, and right now I have to undock things and redock them. Sometimes this isn't possible, so my options become limited.

Badebadebadee, That's all folks!