Wedge Gaussian Load Wrapper

[teubert]

Requirement Text
Update Gaussian load wrapper to support Gaussian load that increases liberally with time

Background Information
Currently Gaussian load wrapper adds Gaussian load with a set standard deviation. Sometimes it is beneficial to have the magnitude of the load increase. This represents how uncertainty in the load increases as you get further out.

Suggested Solution
Argument called std_slope, where std = self.std + std_slope * t

DoD

• Implement feature
• Add to example
• Add tests
• update documentation
• Add to change notes for next release