Add Extent API to get the single OML Module

Resolving OMLZips requires building an acyclic dependency graph such that tables can be resolved by topological traversal of this graph.

Suppose there are two OML Modules: m1 and m2 with an OML ModuleEdge from m1 to m2; which means:
- There is some OML LogicalElement in m1 that cross-references some OML LogicalElement in m2.
- There are no cross-references from any OML LogicalElement in m2 to any OML LogicalElement in m1.
Then, the resolution of m2's tables must complete before the resolution of m1's tables.

JPL-IMCE / gov.nasa.jpl.imce.oml.tables