Fix zoom-to-feature annoyances

* Zoom to feature only if map parameter isn't also
  specified.
* Don't zoom too far in (>z20). Fixes #1511.
* Don't zoom too far out (<z16). Fixes #1522.

js/id/behavior/hash.js

@@ -40,12 +40,14 @@ iD.behavior.Hash = function(context) {
     // the hash can declare that the map should select a feature, but it can
     // do so before any features are loaded. thus wait for the feature to
     // be loaded and then select
-    function willselect(id) {
-        context.connection().loadEntity(id, function(error, entity) {
-            if (entity) {
-                context.map().zoomTo(entity);
-            }
-        });
+    function willselect(id, hasMap) {
+        if (!hasMap) {
+            context.connection().loadEntity(id, function(error, entity) {
+                if (entity) {
+                    context.map().zoomTo(entity);
+                }
+            });
+        }
 
         context.map().on('drawn.hash', function() {
             if (!context.hasEntity(id)) return;
@@ -71,7 +73,7 @@ iD.behavior.Hash = function(context) {
 
         if (location.hash) {
             var q = iD.util.stringQs(location.hash.substring(1));
-            if (q.id) willselect(q.id);
+            if (q.id) willselect(q.id, q.map);
             hashchange();
             if (q.map) hash.hadHash = true;
         }

js/id/renderer/map.js

@@ -350,10 +350,11 @@ iD.Map = function(context) {
         return redraw();
     };
 
-    map.zoomTo = function(entity) {
+    map.zoomTo = function(entity, zoomLimits) {
         var extent = entity.extent(context.graph()),
             zoom = map.extentZoom(extent);
-        map.centerZoom(extent.center(), zoom);
+        zoomLimits = zoomLimits || [16, 20];
+        map.centerZoom(extent.center(), Math.min(Math.max(zoom, zoomLimits[0]), zoomLimits[1]));
     };
 
     map.centerZoom = function(loc, z) {