Fix for issue #26: BeamDyn initialization with non-zero initial azimuth
Fix for issue #26: BeamDyn initialization with non-zero initial azimuth

The initial translation velocity calculation didn't remove the location of the root node when taking the cross product with the rotational velocity. This fixes https://github.com/OpenFAST/openfast/issues/26
OpenFAST/OpenFAST,OpenFAST/OpenFAST,OpenFAST/OpenFAST