Fix ValueStructureEdges traversal in generators

EDG/src/main/java/edg/constraint/AccessConstraint.java

EDG/src/main/java/edg/constraint/AddNodeConstraint.java

EDG/src/main/java/edg/constraint/AsteriskConstraint.java

EDG/src/main/java/edg/constraint/EdgeConstraint.java

EDG/src/main/java/edg/constraint/EmptyConstraint.java

EDG/src/main/java/edg/constraint/GrammarConstraint.java

...main/java/edg/constraint/ListComprehensionConstraint.java

EDG/src/main/java/edg/constraint/PhaseConstraint.java

EDG/src/main/java/edg/constraint/SeekingConstraint.java

EDG/src/main/java/edg/constraint/StructuralConstraint.java

EDG/src/main/java/edg/slicing/ConstrainedAlgorithm.java

e-Knife/src/main/java/eknife/erlang/ValueEdgeGenerator.java