Expand the relationship storage

[GregSal]

Expand the relationship information storage:

• slice_relationship should now contain both a per_region DE-27IM relationship and an aggregated per slice DE-27IM relationship.
• Populate it in the same pass where relationships are computed.
• Modify the current functions accessing slice_relationship so that they work the same as they do now.
• Add two functions that take a slice index and a relationship pair as parameters and return 1) the DE-27IM integer, and 2, the DE-27IM RelationshipType
• Add a function that takes a region_pair and queries contour_lookup, returning a table with the index being the SliceIndex, the columns being the RegionIndex and the values being a list of contours for that region on that slice. Use an empty list of there are no contours for that region on that slice.