[IMP] web: allow to clear the cache in data manager

Sometimes, we need better control on the cache.  For example, if a view or an
action has been changed, it is required to make sure that the correct
data is loaded.

addons/web/static/src/js/framework/data_manager.js

@@ -9,6 +9,10 @@ var utils = require('web.utils');
 return core.Class.extend({
     init: function () {
         this.Filters = new Model('ir.filters');
+        this._init_cache();
+    },
+
+    _init_cache: function () {
         this._cache = {
             actions: {},
             fields_views: {},
@@ -18,6 +22,14 @@ return core.Class.extend({
         };
     },
 
+    /**
+     * Invalidates the whole cache
+     * Suggestion: could be refined to invalidate some part of the cache
+     */
+    invalidate: function () {
+        this._init_cache();
+    },
+
     /**
      * Loads an action from its id or xmlid.
      *