Add possibility to load external data as mercator tiles, add bbox tile possibilities, add CRAB and GRB as datasources in the GRB theme

assets/themes/grb_import/README.md

@@ -0,0 +1,20 @@
+ GRB Import helper
+===================
+
+
+Preparing the CRAB dataset
+--------------------------
+
+````
+# The original data is downloaded from https://download.vlaanderen.be/Producten/Detail?id=447&title=CRAB_Adressenlijst# (the GML-file here )
+wget https://downloadagiv.blob.core.windows.net/crab-adressenlijst/GML/CRAB_Adressenlijst_GML.zip
+        
+# Extract the zip file
+unzip CRAB_Adressenlijst_GML.zip
+
+# convert the pesky GML file into geojson
+ogr2ogr -progress -t_srs WGS84 -f \"GeoJson\" CRAB.geojson CrabAdr.gml
+
+# When done, this big file is sliced into tiles with the slicer script
+node --max_old_space_size=8000 $(which ts-node) ~/git/MapComplete/scripts/slice.ts CRAB.geojson 18 ~/git/pietervdvn.github.io/CRAB_2021_10_26 
+````

assets/themes/grb_import/grb.json

@@ -22,7 +22,7 @@
   "socialImage": "",
   "layers": [
     {
-      "id": "grb-fixmes",
+      "id": "osm-fixmes",
       "name": {
         "nl": "Fixmes op gebouwen"
       },
@@ -198,6 +198,43 @@
       },
       "wayHandling": 2,
       "presets": []
+    },
+    {
+      "id": "crab-addresses 2021-10-26",
+      "source": {
+        "osmTags": "HUISNR~*",
+        "geoJson": "https://raw.githubusercontent.com/pietervdvn/pietervdvn.github.io/master/CRAB_2021_10_26/tile_{z}_{x}_{y}.geojson",
+        "#geoJson": "https://pietervdvn.github.io/CRAB_2021_10_26/tile_{z}_{x}_{y}.geojson",
+        "geoJsonZoomLevel": 18,
+        "maxCacheAge": 0
+      },
+      "minzoom": 19,
+      "name": "CRAB-addressen",
+      "title": "CRAB-adres",
+      "icon": "circle:#bb3322",
+      "iconSize": "15,15,center",
+      "tagRenderings": [
+        "all_tags",
+        {
+          "id": "import-button",
+          "render": "{import_button(addr:street=$STRAATNM; addr:housenumber=$HUISNR)}"
+        }
+      ]
+    },
+    {
+      "id": "GRB",
+      "source": {
+        "geoJson": "https://betadata.grbosm.site/grb?bbox={x_min},{y_min},{x_max},{y_max}",
+        "geoJsonZoomLevel": 18,
+        "mercatorCrs": true,
+        "maxCacheAge": 0
+      },
+      "name": "GRB geometries",
+      "title": "GRB outline",
+      "minzoom": 19,
+      "tagRenderings": [
+        "all_tags"
+      ]
     }
   ],
   "hideFromOverview": true,