Remove vestigial direction-sorting machinery from PathSearch
Pathfinder: Only consider useful neighbors

Depending on the direction we came from, many neighbors are completely
useless. This is the first step to implementing the ideas in 'Jump Point
Search'

V2: Added comment describing what the array is for.
Remove enemy territory avoidance in FindResources.

This is called from the inner loop of the pathfinder, so cannot afford
to do actor queries etc. It also didn't have the desired effect --
harvesters still wander through enemy territory even with the bias.

Just rip it out for a perf win.
Merge pull request #6986 from chrisforbes/minimal-neighbors

Prune neighbor sets based on direction we arrived at a cell