Add a calculation service so that users can run base time-value and forecasting functions

[hoeyi]

Statement

As a user, I can interact with a calculation service that handles basic time-value and forecasting functions, so that I can better plan financial decisions.

Acceptance Criteria

The following functions should be included:

• [x] Future-value: Calculates the future value of a series of cash flows.
• [x] Time-weighted return: Calculates the cumulative return of a series of sub-period returns.
• [x] Annualized return: Calculates the annualized return of a given cumulative return.
• [x] Effective rate: Calculates the effective rate of a given nominal rate and number of periods.