Rework download area support (#908)

Closes #904
* Make all data-related targets like `download*`, `import-osm`, `import-borders`, and `generate-tiles` into `area`-aware -- making it possible for multiple data files to coexist inside the `./data` dir.
* Add `make download area=... [url=...]` command to automatically download any kind of area by checking Geofabrik, BBBike, and OSM.fr, optionally from a custom URL. Supports `area=planet` too.
* Do not re-download area with `make download-*` if it already exists.
* Automatically rename `<area>-latest.osm.pbf` into `<area>.osm.pbf`
* If `area=...` parameter is not given to `make`, see if there is exactly one `*.osm.pbf` file, and if so, use `*` as the `area`.
* Configure many variables in the .env file, overriding the defaults in tools
* If `<area>.osm.pbf` exists, but `<area>.dc-config.pbf` is missing, generate it using `download-osm make-dc` command.

Also:
* closes #614
* closes #647
* partially addresses #261

.env

@@ -24,3 +24,14 @@ FILTER_MAPNIK_OUTPUT=1
 # Some area data like openstreetmap.fr can contain invalid references
 # that must be cleaned up before using it for borders -- set it to true.
 BORDERS_CLEANUP=false
+
+# The current setup assumes this file is placed inside the data/ dir
+MBTILES_FILE=tiles.mbtiles
+# This is the current repl_config.json location, pre-configured in the tools Dockerfile
+# Makefile and quickstart replace it with the dynamically generated one, but we keep it here in case some other method is used to run.
+IMPOSM_CONFIG_FILE=/usr/src/app/config/repl_config.json
+
+# import-borders temp files - set them here to defaults, and override in the Makefile based on the area
+BORDERS_CLEANUP_FILE=data/borders/cleanup.pbf
+BORDERS_PBF_FILE=data/borders/filtered.pbf
+BORDERS_CSV_FILE=data/borders/lines.csv