[PLAT-3816] Curve historical time series functions now ask for price index time series for inflation nodes
[PLAT-3810] Adding USD price index conventions for testing
[PLAT-3820] First attempt at a function to calculate price index curves.

This function assumes that any discounting curves that are needed are supplied exogenously.
[PLAT-3834] Adding a formatter for price index curves
[PLAT-3816] Turning down the logging level