Remove and replace deprecated map/reducer classes. 

This pull request updates all remaining operations that used the deprecated
Reducer1, Reducer2, tiles.Reducer1, and tiles.ThoroughputLimitedReducer1
classes.  This resolves the warnings and makes updating the Raster interface
to remove getTileOpList more straightforward.

This pull request also includes two new operations for getting a sequence of operations that load the tiles of a raster.