Complete Wedge load feature

[teubert]

Complete feature where uncertainty in future loading increases with time (i.e., wedge load, #97).

It's been implemented using linearly increasing load. In the v1.6 release review there was some question about if load should be increasing by sqrt(dt) instead. All mention of the feature was removed so this can be resolved.

See also: https://ntrs.nasa.gov/api/citations/20190000066/downloads/20190000066.pdf (Section 3)

D.o.D.

• Design decision: Wedge load as sqrt or linear
• Add to next release notes
• Add documentation.