Common problems

[GiggleLiu]

This issue is for recording common problems, to get prepared for a final check

• Improper shorthand notation
• bibtex errors
• paper example not shown in unit test/examples folder, causing inconsistency.
• Examples can be poorly shown.
• Some variants do not have example instance.

[GiggleLiu]

Missing canonical model examples (no models.json entry)

The following 10 problems have hand-written paper examples but no canonical_model_example_specs() registration, so they cannot be migrated to load-model-example():

1. GraphPartitioning
2. OptimalLinearArrangement
3. BinPacking
4. Knapsack
5. RuralPostman
6. SubgraphIsomorphism
7. LongestCommonSubsequence
8. SubsetSum
9. MinimumFeedbackArcSet
10. FlowShopScheduling

Each needs a canonical_model_example_specs() function added to its model file and registered in the parent mod.rs, then make examples will include it in models.json and the paper example can be rewritten to use load-model-example().

Context: PR #603 migrated all 28 other problem-def examples to load from models.json via load-model-example().