- Moves Operational Curve shift calculations into their own module
- Refactor into separate curve specific functions
  (with underlying more generic private functions)

This change improves readability and ease of adding further curve shift
calculations.

In similar way that power curve, rpm and pitch shifts are already
calculated, this change adds wind speed shift to the ops curve shift
module

Display the sign (+/-) of the curve shift value in the log warning
message for clarity of the actual shift rather than just displaying the
abs() value that is used when determining whether to raise a log warning