This allows for easier continuous actions, and I think is more intuitive

This was, in fact, completely broken for switching actions.

This is... ridiculous, but it happend to be required by the
Bevy Parenting system. Without this, the Thinker will be randomly
removed from the hierarchy :(

Fixes: https://github.com/zkat/big-brain/issues/13

Fixes: https://github.com/zkat/big-brain/issues/12

I *think* this fixes it, but I need to test it more
thoroughly and make sure everything is actually ok

Fixes: #7 

Fixes: https://github.com/zkat/big-brain/issues/3