Speedup accessing locations for large Inputs

Inputs with many locations causes a large amount of data to be
duplicated when getLocations() is called. Return the vector by reference
instead.
Create InputGrid scheme
Allow forecasts to be produced for datasets without Obs

Previously, the program aborts when attempting to produce forecasts for
non-Obs locations. For non-Obs locations, a missing obs is used in the
Outputs.
Add DownscalerNearestElevation
Folder containing sinusoidal dataset had the wrong name

Rename inputs/bogus to inputs/sine