New generate-dc-config target, rm QUICKSTART_MIN/MAX_ZOOM (#915)

* Set `MAX_ZOOM` to 7 by default.
* Remove `QUICKSTART_MIN/MAX_ZOOM` - unneeded complexity with two env vars. We can just use `MIN_ZOOM` and `MAX_ZOOM`. See also #261
* Generate dc-config yaml file with a new `make generate-dc-config` step. It will compute BBOX based on the downloaded data file. This step is not needed for planet generation.
* Generate Imposm replication file only when `DIFF_MODE` is `true`. Not needed otherwise. If the data source does not support it, it will throw an error.

quickstart.sh

@@ -33,7 +33,7 @@ set -o nounset
 # ./quickstart.sh Adelaide bbbike
 # ....
 #
-# to list geofabrik areas:  make download-geofabrik-list
+# to list geofabrik areas:  make list-geofabrik or make list-bbbike
 # see more QUICKSTART.md
 #
 
@@ -261,6 +261,15 @@ echo "--------------------------------------------------------------------------
 echo "====> : Testing PostgreSQL tables to match layer definitions metadata"
 make test-perf-null
 
+echo " "
+echo "-------------------------------------------------------------------------------------"
+if [[ "$area" != "planet" ]]; then
+  echo "====> : Compute bounding box for tile generation"
+  make generate-dc-config
+else
+  echo "====> : Skipping bbox calculation when generating the entire planet"
+fi
+
 echo " "
 echo "-------------------------------------------------------------------------------------"
 echo "====> : Start generating MBTiles (containing gzipped MVT PBF) from a TM2Source project. "