Makefile target cleanup, minor improvements (#821)

* allow postgres image to be overwritten with an env var
* allow DIFF_MODE var to be overwritten with an env var
* add /mapping and /cache dirs into tools image
* make `build-sql` target explicit rather than relying on a filename
* `tools-dev` will open a shell in a docker to experiment and debug (instead of `import-sql-dev` and `import-osm-dev`)
* separated `start-maputnik` from `start-postserve`
* renamed `clean-docker` into `db-destroy` to make it more explicit
* cleaner `db-start`, `db-stop`, `db-destroy` targets
* better output messages

docker-compose.yml

@@ -11,7 +11,7 @@ networks:
 services:
 
   postgres:
-    image: "openmaptiles/postgis:${TOOLS_VERSION}"
+    image: "${POSTGIS_IMAGE:-openmaptiles/postgis}:${TOOLS_VERSION}"
     volumes:
       - pgdata:/var/lib/postgresql/data
     networks:
@@ -71,12 +71,16 @@ services:
       # Must match the version of this file (first line)
       # download-osm will use it when generating a composer file
       MAKE_DC_VERSION: "2.3"
+      # Allow DIFF_MODE to be overwritten from shell
+      DIFF_MODE: ${DIFF_MODE}
     networks:
       - postgres_conn
     volumes:
       - .:/tileset
       - ./data:/import
       - ./build:/sql
+      - ./build:/mapping
+      - ./cache:/cache
 
   generate-changed-vectortiles:
     image: "openmaptiles/generate-vectortiles:${TOOLS_VERSION}"