Adding HAWC2 monopile and VolturnUS-S CAD

[gbarter]

Purpose

100% of credit to @jennirinker for the work involved in getting us to:

• HAWC2 model of the monopile
• Alignment of HAWC2, OpenFAST, YAML tower and monopile discretizations (with CI tests)

Also credit to Alastair Ramsay for:

• Community addition of UMaine VolturnUS-S Solidworks model

Type of change

• [x] Bugfix (non-breaking change which fixes an issue)
• [x] 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

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

[gbarter]

@jennirinker : Anything to add to the Release Notes?

[jennirinker]

Release notes look good! I just want to link in this comment to Pull Requests #149 and #153 in case someone wants to read more about the specifics of the tower/monopile structural updates. I'll do a quick (final) review and then mark this as ready.