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/icons/cliff2.svg

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   version="1.1"
+   id="svg2"
+   height="11"
+   width="15">
+  <defs
+     id="defs4" />
+  <metadata
+     id="metadata7">
+    <rdf:RDF>
+      <cc:Work
+         rdf:about="">
+        <dc:format>image/svg+xml</dc:format>
+        <dc:type
+           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
+        <dc:title></dc:title>
+      </cc:Work>
+    </rdf:RDF>
+  </metadata>
+  <g
+     transform="translate(0,-5)"
+     id="layer1">
+    <path
+       id="path2988"
+       transform="translate(0,5)"
+       d="m 0,5 c 0,0.75 -3.74999e-5,0.25 0,1 l 5,0 2,5 1,0 2,-5 5,0 0,-1 z"
+       style="fill:#999999;fill-opacity:1;stroke:none" />
+    <path
+       style="fill:none;fill-opacity:1;stroke:none"
+       d="m 5.0000001,10 2,-5 1.0000001,0 1.9999997,5 z"
+       id="path3413" />
+  </g>
+</svg>