compiles with DirT replaced by an enum but 3 tests fail

[calbaker]

python sim_manager_demo.py on fix/change-DirT-to-enum

python sim_manager_demo.py 
Elapsed time to import rail vehicles, locations, and network: 0.088 s
Entering `sim_manager` module.
2024-02-14 13:31:47
/Users/cbaker2/Documents/Projects/altrios/altrios_code/python/altrios/resources/Default Demand.csv
Elapsed time to plan train consist for year 2022: 25 s
Elapsed time to run dispatch for year 2022: 0.497 s
Elapsed time to run `sim_manager.main()`: 25.5 s
Elapsed time to run train sims: 2.05 s
Elapsed time to build and run summary sims: 2 s
Elapsed time to run `tolist()`: 0.00347 s
Elapsed time to get total fuel energy: 7.08e-06 s
Total fuel energy used: 1.96e+03 GJ
Total fuel used: 1.18e+04 gallons

python sim_manager_demo.py on main

Elapsed time to import rail vehicles, locations, and network: 0.0907 s
Entering `sim_manager` module.
2024-02-14 13:35:04
/Users/cbaker2/Documents/Projects/altrios/altrios_code/python/altrios/resources/Default Demand.csv
Elapsed time to plan train consist for year 2022: 25 s
Elapsed time to run dispatch for year 2022: 0.497 s
Elapsed time to run `sim_manager.main()`: 25.5 s
Elapsed time to run train sims: 2.03 s
Elapsed time to build and run summary sims: 1.98 s
Elapsed time to run `tolist()`: 0.00394 s
Elapsed time to get total fuel energy: 2.43e-05 s
Total fuel energy used: 1.96e+03 GJ
Total fuel used: 1.18e+04 gallons

Conclusion

This PR makes the code more readable and maintainable without any obvious computational penalty.