simple path-finding flag for units

[withers]

Currently when we add entities of type "unit", they use biter logic, which means they try to navigate around things to reach a target. This is causing some headache with my mod "followers", as it becomes difficult for a follower to navigate around a large base with lots buildings and belts all over the place. (especially belts)
It would be terrific if we could give units a simple "as the crow flys" path-finding flag, so that units we create with also the "not-on-map" flag can just fly straight to the target, like logisctic bots and construction bots.