Pxx Calculations

[dtarin]

It would be useful to see some additional features for the uncertainty tool and I would like to suggest the following. 

1. Allow more user-defined fields for which p-factors to include. There is P50 default, with two additional entries for the user to define. It is common to include P50, P75, P90, P95, and P99 in financial analyses and reporting to Independent Engineers. Therefore, the request is to increase the number of user-defined p-factors available, while not forcing the user to use all of them (a toggle button to activate/deactivate).
2. Allow the units to be changed from GWh to kWh or MWh.
3. Allow this data to be exported (to image or excel), similar to how we can export other data such as the shading table or monthly meteo table. 
4. Allow the user to define whether the results are expressed in energy or in terms of percentages, both under Annual production probability, and on the chart. It is common in industry to post-process for additional considerations outside of PVsyst, so the energy values shown are meaningless/misleading, but the uncertainty tool can still be useful for reporting, especially since the uncertainty calculations themselves are independent. If we are able to export or screenshot the results displaying percentages, it would find more utility. 
   • i.e., P50 - 100%, P90 - 92.4%, P99 - 86.4%, etc.