Fixed edge weight additions for Dijkstra's

Move the processing of the graph to the point in AtlantisEntity where
the navigation actually starts. Previously, graph was processed too
early. Warning messages printed for entity walking through terrain
should be removed for production, but these will be left for now to spot
problems.
Merge branch 'issue36' into develop
Merge branch 'develop' of git@github.com:gsnorton/CS-547-Project-Two.git into develop
Marked issue36 as complete
Merge branch 'issue36' into develop