Add `build-style` and `download-fonts` targets. (#1445)

This PR adds `build-style` and `download-fonts` targets to `start-tileserver` target. 

Calling `build-style` and `download-fonts` ensures that there is the OSM OpenMapTiles style build and ready and fonts downloaded.

Makefile

@@ -480,7 +480,7 @@ generate-changed-tiles: data/tiles.txt
 	fi
 
 .PHONY: start-tileserver
-start-tileserver: init-dirs
+start-tileserver: init-dirs build-style download-fonts
 	@echo " "
 	@echo "***********************************************************"
 	@echo "* "