Add a Translate interaction

This allows features to be moved around the map. It works much like the Modify interaction, however it's significantly simpler. It uses the geometry's underlying `translate` function.

externs/olx.js

@@ -2504,6 +2504,22 @@ olx.interaction.DrawOptions.prototype.freehandCondition;
 olx.interaction.DrawOptions.prototype.wrapX;
 
 
+/**
+ * @typedef {{features: (ol.Collection.<ol.Feature>|undefined)}}
+ * @api
+ */
+olx.interaction.TranslateOptions;
+
+
+/**
+ * Only features contained in this collection will be able to be translated. If
+ * not specified, all features on the map will be able to be translated.
+ * @type {ol.Collection.<ol.Feature>|undefined}
+ * @api
+ */
+olx.interaction.TranslateOptions.prototype.features;
+
+
 /**
  * @typedef {{condition: (ol.events.ConditionType|undefined),
  *     duration: (number|undefined),