leaflet update (#78)

**This PR is created to track progress of leaflet update to v1.4.0.**

Before merging into master I want to figure out if we need these changes:
* [ ] McBen@b5b33fb#diff-66cb4ebaec98b864101ad1f5bcbda09e
  (even if we need this, I suppose that more cleaner way is to extend `L.Popup` in [`oms.js`] 
* [x] #69 (Do we ever need monkey patching here?)
* [x] 67c1741
  Do we need **replace** default icons? Wouldn't it be better just add our icons with own names?

Even after merge I propose do not delete the branch, in order to easy view our modifications to the external's code (see #70).

[`oms.js`]: https://github.com/IITC-CE/ingress-intel-total-conversion/blob/master/code/oms.js

code/boot.js

@@ -176,6 +176,7 @@ window.setupMap = function() {
     bounceAtZoomLimits: false,
     preferCanvas: true // Set to true if Leaflet should draw things using Canvas instead of SVG
   });
+  if (L.CRS.S2) { map.options.crs = L.CRS.S2; }
 
   if (L.Path.CANVAS) {
     // for canvas, 2% overdraw only - to help performance
@@ -636,6 +637,35 @@ window.extendLeaflet = function() {
     return new L.DivIcon.ColoredSvg(color, options);
   };
 
+  /* !!This block is commented out as it's unclear if we really need this patch
+
+  // See https://github.com/IITC-CE/ingress-intel-total-conversion/issues/122
+
+  // use the earth radius value used by the s2 geometry library
+  // this library is used in the ingress backend, so distance calculation, etc
+  // are far closer if we use the value from that
+
+  L.CRS.Earth.R = 6367000;
+
+  var s2SphericalMercator = L.Util.extend({}, L.Projection.SphericalMercator, {
+    R: window.EARTH_RADIUS,
+    bounds: (function () {
+      var d = window.EARTH_RADIUS * Math.PI;
+      return L.bounds([-d, -d], [d, d]);
+    })()
+  });
+
+  L.CRS.S2 = L.Util.extend({}, L.CRS.Earth, {
+    code: 'EPSG:S2',
+    projection: s2SphericalMercator,
+    transformation: (function () {
+      var scale = 0.5 / (Math.PI * s2SphericalMercator.R);
+      return L.transformation(scale, 0.5, -scale, 0.5);
+    }())
+  });
+
+  */
+
   // Fix Leaflet: handle touchcancel events in Draggable
   L.Draggable.prototype._onDownOrig = L.Draggable.prototype._onDown;
   L.Draggable.prototype._onDown = function(e) {