Updates based on WES reviewer comments

[nikhar-abbas]

Description and Purpose

This brings in some updates that have been made based on reviewer comments to the WES-preprint about ROSCO:
https://wes.copernicus.org/preprints/wes-2021-19/

Two major changes:

1. Use the nacelle fore-aft translational velocity signal rather than the nacelle fore-aft angular velocity for the floating feedback term to be more consistent with the standard bladed interface
2. Update the controller tuning methods so that the system pole is modified in above-rated operation when the generator torque controller is set to constant-power operation

One minor change:

1. The TSR was not saturated properly in region 2.5, so it would stay constant even though the wind speed would be increasing and the rotor speed was constant. Now the TSR drops appropriately.

Type of change

What types of change is it?
Select the appropriate type(s) that describe this PR

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Github issues addressed, if one exists

Examples/Testing, if applicable

Standard tests should pass