[PetraAI] - Send the construction party before placing foundation.

[Freagarach]

As noted on the forums (​https://wildfiregames.com/forum/topic/55812-suggestion-make-new-building-orders-by-ai-invisible-to-human-player/) PetraAI often plans constructions on the other side of the map and then picks builders to work on it. It would be nice if she would send a construction party first and only lay the foundation when they have (almost) arrived.