New methods to work with distributions

Kolmogorov-Smirnov test method (kstest) for Portfolio and AssetList.

New forecasting methods for Portfolio:

• percentile_inverse
• percentile_from_history
• forecast_wealth_history
• forecast_monte_carlo_cagr
• forecast_wealth

Some of the old forecasting methods are renamed.

New Plotting methods for forecasts in Portfolio:

• plot_forecast
• plot_forecast_monte_carlo
• plot_plot_hist_fit
• plot_percentiles_fit

New notebooks with examples:
04 backtesting distribution.ipynb
05 forecasting.ipynb