IEC Kaimal recoded up

[ptrbortolotti]

I recoded the script of aeroelasticse where the turbulent wind IEC Kaimal spectrum is computed, adding a regression test and removing legacy code

Purpose

Support Level 1 activities

Type of change

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• 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)

Testing

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Checklist

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• I have run existing tests which pass locally with my changes
• I have added new tests or examples that prove my fix is effective or that my feature works
• I have added necessary documentation

[dzalkind]

@ptrbortolotti, I updated the example to check our spectra against TurbSim.

[dzalkind]

Let's keep this open while we figure out the rotor average spectrum.

[dzalkind]

I think this is good to go. Thanks @ptrbortolotti and all!