Add addInteraction and removeInteraction methods to the map

This is in line with how we add/remove controls and overlays.

src/ol/map.js

@@ -350,6 +350,14 @@ ol.Map = function(options) {
         control.setMap(this);
       }, this);
 
+  this.interactions_.forEach(
+      /**
+       * @param {ol.interaction.Interaction} interaction Interaction.
+       */
+      function(interaction) {
+        interaction.setMap(this);
+      }, this);
+
   this.overlays_.forEach(
       /**
        * @param {ol.Overlay} overlay Overlay.
@@ -375,6 +383,18 @@ ol.Map.prototype.addControl = function(control) {
 };
 
 
+/**
+ * Add the given interaction to the map.
+ * @param {ol.interaction.Interaction} interaction Interaction to add.
+ */
+ol.Map.prototype.addInteraction = function(interaction) {
+  var interactions = this.getInteractions();
+  goog.asserts.assert(goog.isDef(interactions));
+  interactions.push(interaction);
+  interaction.setMap(this);
+};
+
+
 /**
  * Adds the given layer to the top of this map.
  * @param {ol.layer.Base} layer Layer.
@@ -953,6 +973,24 @@ ol.Map.prototype.removeControl = function(control) {
 };
 
 
+/**
+ * Remove the given interaction from the map.
+ * @param {ol.interaction.Interaction} interaction Interaction to remove.
+ * @return {ol.interaction.Interaction|undefined} The removed interaction (or
+ *     undefined if the interaction was not found).
+ */
+ol.Map.prototype.removeInteraction = function(interaction) {
+  var removed;
+  var interactions = this.getInteractions();
+  goog.asserts.assert(goog.isDef(interactions));
+  if (goog.isDef(interactions.remove(interaction))) {
+    interaction.setMap(null);
+    removed = interaction;
+  }
+  return removed;
+};
+
+
 /**
  * Removes the given layer from the map.
  * @param {ol.layer.Base} layer Layer.