Fix errors in OpenFAST floating files

The Elastodyn tower mode shapes in the floating version were causing an instability and the platform center of mass value was incorrect. These have been corrected and noted in the release notes.

IEA Wind 15-MW Reference Wind Turbine update

IEA Wind Task 37 is proud to release an update to its 15-MW Reference Wind Turbine. A detailed list of changes is provided in the release notes. Many of these updates were driven by community engagement, so we are appreciative of everyone that has taken the time to document the issues and give us feedback.

Switch to versioning of the RWT

This release tags the master branch as the design which corresponds to the published reports. This also signals that updates will be coming that address some of the design issues and model input issues identified by the community.