New features for unsteady aerodynamics modeling

[bjonkman]

Feature or improvement description
This pull request includes the following new features:

• UnsteadyAero can be turned off based on a node's radial location (as opposed to setting c_nalpha = 0 in individual airfoil files). Two new lines in the AeroDyn input file allow the user to specify the radial locations where unsteady aero will be on.
• DBEMT_Mod = 3 is now available for time-marching simulations.
• UAMod = 4 (HGM) is now available for time-marching simulations.
• A new UAMod = 5 option is available. This model is based on HGM with one additional state.
• Airfoil tables can now be constant (i.e., have fewer than 3 lines). UA is turned off for constant airfoil tables.
• The UA parameters listed in the Airfoil files can now be calculated internally instead of user-specified. If any of the lines containing UA parameters are missing from the file, they get set by the code.

Related issue, if one exists
None

Impacted areas of the software
AeroDyn

Additional supporting information

• I also added some more validity checks on AFI UA parameters

Test results, if applicable
These changes do not change any existing test cases. All changes to the input file are optional.

[andrew-platt]

@rafmudaf and @ebranlard
Should we merge this into the RC3.1 branch instead of dev? That way we can keep the current dev as the 3.0 release (hopefully releasing soon).

[ebranlard]

As a small note, I've merged this branch with f/driver into my branch f/driver-ua, where I've added two other dynamic stall models (Oye and Boeing-Vertol), but it's fine by me if we do this in two pull requests. (Mine will change the polar input file, adding the relative thickness). We might just be both doing the merge with dev..

[andrew-platt]

This looks good to me.

I really like the method of dealing with missing lines in input file parsing. I'll have to use it in other codes.

[ebranlard]

This is al good to me.

I've started using this branch in my branch f/driver-ua and have not seen any issue. We might need to do small adjustments on UAMod 4 and 5 in the future, but nothing that would prevent the merge now.

[ebranlard]

I've added some documentation here.

Which will become available when my branch get's merged. I believe it's fine to wait a couple of months for that.

[bjonkman]

Since #729 was merged into #688, and #688 has subsequently been merged into OpenFAST/dev, the remaining changes here are minimal: some documentation of api changes, comments, and minor code cleanup.