PSY Remaining TODOs for Second Cost Refactor

[GabrielKS]

This is a list of TODOs that remain unfinished from #1071, they should all be addressed before PSY 4 is released.

• Make other fields of MarketBidCost time series, see Initial refactor of cost functions #1071 (comment)
• Nail down naming of everything to both conform to power systems domain conventions and not be misleading about what things are #1123
• Nail down what is part of the public interface (e.g., just the cost aliases or ValueCurves?)
• Do this to support 3 -> 4 system conversions (EDIT: we are no longer committing to implementing all of these):

  PowerSystems.jl/src/data_format_conversions.jl

  Line 107 in 234936e

  # TODO implement remaining _convert_op_cost methods

• Minor TODO(?):

  PowerSystems.jl/test/test_constructors.jl

  Line 24 in 234936e

  # TODO add concrete subtypes of ProductionVariableCost?

• Minor TODO:

  PowerSystems.jl/src/PowerSystems.jl

  Line 553 in 234936e

  get_points, # TODO possible rename to disambiguate from geographical information

• Fill in TODOs in https://github.com/NREL-Sienna/PowerSystems.jl/blob/234936ef5e06c47388d560511ec6c817f4f30864/docs/src/modeler_guide/cost_functions.md
• Address Implement pretty print REPL methods for operation cost #1048
• Already covered by other items, but

  PowerSystems.jl/src/models/cost_functions/cost_aliases.jl

  Line 84 in 234936e

  # TODO documentation, more getters, custom printing so it always shows the type alias (like Vector does)

• Finalize decision on cost-related time series getters and setters: currently the setter takes a time series but the getter returns a time array, this is convenient but violates a certain symmetry. See Fuel Cost Interface, Including Time Series #1101 (comment)

[jd-lara]

On the get_points, it isn't too much of a problem since the geographic info uses GeoJSON blobs.

[jd-lara]

#1081 Is also part of this list

[GabrielKS]

wrt "Nail down naming of everything," would someone with a power systems background like to review my naming?

[jd-lara]

@GabrielKS can you update the list and close if this is pretty much ready please?