Rectangular update

[dzalkind]

This PR collects a lot of the open-source developments required for the EAB case studies, including:

• Modeling rectangular members in HydroDyn and SubDyn
• A new hybrid potential_model_override method using potential model for only radiation and excitation (not bouyancy)
• New load cases (force-displacement, free decay, user-defined wind)
• Improved DLC 1.2 support, using probability clusters

Things left TODO:

• Elevate potential_model_override option above RAFT as it affects both RAFT and OpenFAST
• Add various flavors of VolturnUS modeling (rectangular, SubDyn, hybrid)
• Add fatigue example
• Organize pre-processing notebooks (fatigue, orcaflex translator)
• Test all new DLC cases
• Fix SubDyn generation, ElastoDyn mass needs to be zeroed
• Check heave of models
• Check WEIS-generated models against develop branch

Purpose

This PR updates WEIS to generate HydroDyn and SubDyn files for rectangular members. The SubDyn update also applies to circular members.

Type of change

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Select the appropriate type(s) that describe this PR

• New feature (non-breaking change which adds functionality)

Testing

Explain the steps needed to test the new code to verify that it does indeed address the issue and produce the expected behavior.

Checklist

Put an x in the boxes that apply.

• 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

[coveralls]

coverage: 58.377% (+0.2%) from 58.139%
when pulling e31448a on rectangular_update
into 9913da4 on develop.