Fixes

Summary/Motivation:

Changes proposed in this PR:

• Adds Nov 2008 and Sep 2019 CEPCI factors to the registered currency units dictionary
• Significant improvement to physical units handling for process and currency parameters, including allowing users to specify a base year with automatic currency units conversion
• Ensures units consistency across power plant costing methods, and employs new UnitModelCostingBlock syntax
• Variables costs were changed from units of $MM/production (implied for one year) to actual units of $MM/year. Only power production is considered, not hydrogen.

Some other changes:

• Combines costing parameter and exponent dictionaries, and adds bare erected cost currency units for a specific reference year and prefix. For example, dictionaries containing "BEC_units": "K$2018" will tell the costing methods to import the reference costs in kUSD_2018 (Pyomo unit container). Results are reported in MUSD_year, where year is the base year chosen by users.

• Similarly, scaled parameters now automatically get variable units and reference parameter accounts units must use correct Pyomo units syntax.

• Finally, the tests were updated, including the ones using the old costing methods. We will remove those in a future update.

• This will break the current NGCC SOEC example. A fix for this exists in Update NGCC SOEC example for new costing methods examples-pse#151 and should be merged ASAP after merging this PR.

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