Create API endpoints for several different raster operations

[kellyi]

TODO: update this card with more specifics once #3 is complete.

[kellyi]

Path	Service
/localvariety	Returns local variety results
/focalstandarddeviation	Returns focal standard deviation results
/zonalhistogram	Returns zonal histogram results
/pngtile	Returns a PNG tile fit to the shape
/geotiff	Returns a GeoTIFF for the drawn shape along with Raster data

[kellyi]

Server's currently set up to create an S3LayerReader from a catalog. However, it is not currently querying for any specific RDDs from the catalog, and the endpoints don't currently do anything with the data.

Some steps here:

• move the ops out into a separate jobUtils file like the one from mmw-geoprocessing
• set up localvariety endpoint to get counts from one of the RDDs
• figure out the focal and zonal ops replaced this with some count and average operations

[kellyi]

Going to create a new issue for the png/geotiff tile operations:

set up visual tile endpoints such that one uses nlcd and the other uses slope to return a tile cut to the extent of the posted polygon