[IMP] pyeval: implement weekday function

courtesy of mva.  This adds the weekday function to date objects in
pyeval.  This will be useful for adding better filters (such as this
week) in the searchview.

addons/web/static/src/js/pyeval.js

@@ -517,6 +517,9 @@
         toordinal: function () {
             return py.float.fromJSON(ymd2ord(this.year, this.month, this.day));
         },
+        weekday: function () {
+            return  py.float.fromJSON((this.toordinal().toJSON()+6)%7);
+        },
         fromJSON: function (year, month, day) {
             return py.PY_call(datetime.date, [year, month, day]);
         },