WIP: Refactor\fix to local method changes

In refactoring the local operations to be on rasters instead of Op[Raster], there was a change introduced that had operations on Rasters returning Op[Raster]'s, which was incorrect. 

This refactor specifies the return types of the local operations (Raster), and fixes those operations. Some work was done to map and combine on DataSourceLike so that the default now should be that a RasterSource (or LocalOpMethods) would only call 'map' or 'combine', instead of 'mapOp' or 'combineOp'.