Gapfilling meteo data where MDS is not applied (P, PA, WS...) - use original data if ERA are not available in aggregations

[darpap]

Currently, in case ERA are not available and original data are available, in the halfhourly final file there is P (with original data) and P_F is all -9999. This happens even for the days where P is always present. It is ok because in fact the variable is not fully gapfilled.
However this creates a problem in the daily files where the P is always entirely missing even for days where there are measurements.

Let's consider the possibility to provide P_F from daily to yearly in case we have the periods fully covered by measurements (so only for the days->years where there are no gaps)