[FIX] web, web_kanban: make qweb default dict configurable

In a previous refactor, qweb configuration was simplified.  However, I
missed the fact that session.js sneakily configure the qweb instance
after the fact. As a result, the kanban view did not have the _s key in
its custom qweb instance default dict.  This commit allow the qweb class
constructor to add default keys to the instance.

Now, kanban view can add _s, and everything is good.

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

@@ -5,16 +5,16 @@ var translation = require('web.translation');
 
 var _t = translation._t;
 
-function QWeb(debug) {
+function QWeb(debug, default_dict) {
     var qweb = new QWeb2.Engine();
-    qweb.default_dict = {
+    qweb.default_dict = _.extend({}, default_dict || {}, {
         '_' : _,
         'JSON': JSON,
         '_t' : translation._t,
         '__debug__': debug,
         'moment': function(date) { return new moment(date); },
         'csrf_token': odoo.csrf_token,
-    };
+    });
     qweb.debug = debug;
     return qweb;
 }

addons/web_kanban/static/src/js/kanban_view.js

@@ -60,7 +60,7 @@ var KanbanView = View.extend({
     init: function () {
         this._super.apply(this, arguments);
 
-        this.qweb = new QWeb(session.debug);
+        this.qweb = new QWeb(session.debug, {_s: session.origin});
 
         this.limit = this.options.limit || 40;
         this.fields = {};