Tower updates plus first pass at monopile

[jennirinker]

Hello!

This MR includes two main things:

• Some updates to the non-Volturn tower + associated scripts
• A first pass at a monopile model in HAWC2

Tower updates

1. Updated the automatic script in the FixedSubstructure model to properly account for discretization
2. Added a check in said script so it cross-references the Excel tabular data sheet

Monopile model

1. Made a folder for the monopile model
2. Created a similar automatic script as was used in the FixedSubstructure to create the monopile st file (plus one that only starts at the mudline)
3. Made an htc file for the fixed-mudline monopile model with irregular waves as an example

Ready to merge?

Even though the monopile model is a preliminary version, I think it would be okay to merge it and just update the model as people identify bugs. I have no plans at this time to implement a soil model, so I think it would be best to not wait for that.

Thus, this is ready to merge (1) once it is reviewed by someone else and (2) assuming the discretization I use for the tower/monopile in #116 is correct.

[gbarter]

Should this be aimed at master or develop?

[jennirinker]

This is stale now that I'm working on #147 so I'm going to close it