Add y-labels for some verification plots
Added CorrectorClimReg
Add spatial elevation gradient in DownscalerNearestElevation

* Compute elevation gradient when creating locations
* Allow weighting of gradient in DownscalerNearestElevation
* Compute gradient in InputNetcdfCf
Add AveragerMean
Safeguard against no obs input defined
Show gradient information in Info driver
Various uninportant fixes
Added new verification plots