Add biomes as map layer in map service

[oubiwann]

Note: this ticket is being superseded by hexagram30/raster#15 ...

Now that #23 is done, let's integrate it into the map service ...

[oubiwann]

I want to pause on this until #33 is resolved.

[oubiwann]

Actually, #33 has been closed and won't be done. Per #30, a new service is being created to support raster layers. The map project will utilize the following:

• The raster service's networked storage (see Decide upon a KV store raster#3)
• The raster gRPC service (see Implement gRPC API raster#11)
• a Clojure library for the gRPC service (see Create a Clojure KVStore gRPC client project raster#8)

As such, a companion ticket has been created here:

• Add Ilumo layers at 1600x scale raster#15

I will change the description of the current ticket to reflect this ...