Funnel - Loess Regression

The description of the subscreenfunnel function previously entailed the step 
> "use Loess regression to smooth the upper and lower limits of the funnel"

As this was not reflected in the actual subscreenfunnel function, it was deleted from the description.

Long-term the idea is to include the Loess regression to smooth funnel limits in the code and then add it to the description again.