Add MassBalanceMachine Plot Classes

[JulianPBiesheuvel]

Describe the solution you'd like
Added a dedicated .plot class, or classes, containing methods for plotting predictions, maps, and other kinds of graphs, all in one place.

[JulianPBiesheuvel]

• Plot for the climate features, values versus time
• Distributions of cross-validation splits
• Hyperparameter search for the best model (graph displaying the loss per searched value of a single hyperparameter)
• Predictions versus Ground truth
• Plot distributions of the input variables
• Plot glacier attributes (slope, aspect, elevation, dist from border)
• Plot temperature and precipitation aggregated over grid points
• Line plot of the glacier average per year