Add `geoutils.config` parameters for resampling

[rhugonnet]

For raster grid resampling to be always done the same, such as "bilinear", "cubic", etc using reproject(). But also for raster interpolation to points in interp_points() and other functionalities such as xDEM's Coreg module!

Should these 2 resampling be separate, or a single argument? It makes some sense that they should always be consistent between themselves.