Move factory assist state to gadgets.

[GoogleFrog]

With commshare this state needs to be in gadget-world and managed by a gadget. It would be nice for spectating in any case (I could advise people to enable it).

[GoogleFrog]

This is somewhat more important since a gadget version would prevent this bug:

• Player gives order to unit in factory.
• Unit completes.
• Widget detects completion. Notices that player did not override command queue. Gives move move guard order to constructor.
• Player order arrives over network, applied to unit.
• Move move guard arrives over network. Overrides player order.

With a gadget version of factory assist it would never override player orders given to in-construction constructors.