automatically delete other paths when making new units
only allow making child path if parent didn't later make a child unit
make deleteOtherPaths() delete alternate non-live paths made at same time as specified path's ancestor, so there can only be 1 non-live resource total
Merge branch 'simplify-rsc'
dramatically simplify resource calculation
update some comments to reflect simplified resource assumptions
implement population limit, close #38
fix laser implementation breaking loading games
only do resource check in SegmentUnit.delete() if unit that collects resources is deleted

Conflicts:
	Assets/Scripts/SegmentUnit.cs