Adds increased zoom keyboard shortcuts.

js/id/id.js

@@ -264,6 +264,8 @@ window.iD = function () {
     context.pan = map.pan;
     context.zoomIn = map.zoomIn;
     context.zoomOut = map.zoomOut;
+    context.zoomInFurther = map.zoomInFurther;
+    context.zoomOutFurther = map.zoomOutFurther;
 
     context.surfaceRect = function() {
         // Work around a bug in Firefox.

js/id/renderer/map.js

@@ -327,8 +327,19 @@ iD.Map = function(context) {
         return redraw();
     };
 
-    map.zoomIn = function() { interpolateZoom(~~map.zoom() + 1); };
-    map.zoomOut = function() { interpolateZoom(~~map.zoom() - 1); };
+    function zoomIn(integer) {
+      interpolateZoom(~~map.zoom() + integer);
+    }
+
+    function zoomOut(integer) {
+      interpolateZoom(~~map.zoom() - integer);
+    }
+
+    map.zoomIn = function() { zoomIn(1); };
+    map.zoomInFurther = function() { zoomIn(4); };
+
+    map.zoomOut = function() { zoomOut(1); };
+    map.zoomOutFurther = function() { zoomOut(4); };
 
     map.center = function(loc) {
         if (!arguments.length) {

js/id/ui/zoom.js

@@ -33,10 +33,15 @@ iD.ui.Zoom = function(context) {
         _.each(['=','ffequals','plus','ffplus'], function(key) {
             keybinding.on(key, function() { context.zoomIn(); });
             keybinding.on('⇧' + key, function() { context.zoomIn(); });
+            keybinding.on('ctrl+' + key, function() { context.zoomInFurther(); });
+            keybinding.on('ctrl+⇧' + key, function() { context.zoomInFurther(); });
         });
+
         _.each(['-','ffminus','_','dash'], function(key) {
             keybinding.on(key, function() { context.zoomOut(); });
             keybinding.on('⇧' + key, function() { context.zoomOut(); });
+            keybinding.on('ctrl+' + key, function() { context.zoomOutFurther(); });
+            keybinding.on('ctrl+⇧' + key, function() { context.zoomOutFurther(); });
         });
 
         d3.select(document)