OSM OpenMapTiles style (#1420)

* OpenMapTiles style

* Rename style snippets from layer_name.json to defaultstyle.json

* Add README to icons dir.

* Add README to icons dir.

* Rename snippets to style.json

* Fix spritezero - move icons to svg subdir

* Move icons from style/icons/svg directly to style/icons

Co-authored-by: Tomas Pohanka <TomPohys@gmail.com>

style/README.md

@@ -0,0 +1,87 @@
+## OSM OpenMapTiles style
+
+_OSM OpenMapTiles_ is the official style of OpenMapTiles.
+Its purpose is to display all features in vector tiles.
+
+OSM OpenMapTiles style is heavily inspired by 
+[OSM Carto](https://github.com/gravitystorm/openstreetmap-carto).
+
+Huge credit belongs to the original 
+[authors](https://github.com/gravitystorm/openstreetmap-carto/blob/master/LICENSE.txt).
+
+### Fonts
+
+OSM OpenMapTiles style used _Noto Sans_ fonts. 
+To download these fonts run:
+```bash
+make download-fonts
+```
+It downloads _Noto Sans_ fonts (~70MB) and extract them into [openmaptiles/data/fonts](../data/fonts) directory.
+
+### Icons/sprite
+
+All icons which are used OpenMapTiles style are located in [openmaptiles/style/icons](icons). 
+After the style is built, the icons are composed into sprite files located in `build` directory. 
+
+Additional svg icons can be added to [openmaptiles/style/icons](icons) directory. 
+
+To generate new sprite files with added icons, run: 
+```bash
+make build-sprite
+``` 
+Sprite files will be generated into `build` directory.
+
+### OSM Icons
+
+Icons in the _OSM OpenMapTiles_ style are based on original 
+[OSM Carto](https://github.com/gravitystorm/openstreetmap-carto) symbols.
+
+The original icons can be found in 
+[openstreetmap-carto/symbols](https://github.com/gravitystorm/openstreetmap-carto/tree/master/symbols).
+
+Icons used in _OSM OpenMapTiles_ style were scaled down and saved as svg.
+
+### Build style
+
+To build style run:
+```bash
+make build-style
+```
+It generates new sprite files and merges all style snippets from each layer, orders them according the `order` value 
+and saves the complete style into `build/style/style.json`.
+
+### Tileserver-gl
+The tileserver serves both the tiles and the OSM OpenMapTiles map. 
+#### MBTiles (default)
+By default, the tileserver serves OSM OpenMapTiles map based on tiles from `data/tiles.mbtiles` as defined in 
+[style-header.json](./style-header.json).
+```json
+"sources": {
+  "openmaptiles": {
+    "type": "vector",
+    "url": "mbtiles:///data/tiles.mbtiles"
+  },
+  ...
+}
+```
+#### Serve from the db
+The tileserver can also serve OSM OpenMapTiles map based on dynamically generated tiles directly from the database. 
+Start the database container and the postserve container: 
+```bash
+make start-db
+make start-postserve
+```
+In [style-header.json](./style-header.json) change the source of tiles to PostServe:
+
+#### Start tileserver
+Before you start the tileserver, make sure you have fonts downloaded in [openmaptiles/data/fonts](../data/fonts), 
+sprites generated and style built:
+```bash
+make download-fonts
+make build-style
+```
+Start tileserver:
+```bash
+make start-tileserver
+```
+And go to http://localhost:8080.