[REF] web: update widget to new guidelines

- make delegate/undelegate events private
- remove $el before start
- make replaceElement private
- remove one _ from __render_and_insert... method
- update documentation
- remove make and improve make_descriptive (also, it is private)
- ...

addons/web/static/src/js/fields/basic_fields.js

@@ -438,7 +438,7 @@ var FieldDate = InputField.extend({
             def = this.datewidget.appendTo('<div>').done(function () {
                 self.datewidget.$el.addClass(self.$el.attr('class'));
                 self._prepareInput(self.datewidget.$input);
-                self.replaceElement(self.datewidget.$el);
+                self._replaceElement(self.datewidget.$el);
             });
         }
         return $.when(def, this._super.apply(this, arguments));