[FIX] web: allow to group on more groupable fields with the searchview

Some fields are groupable even though they are not stored (e.g. an inherited
field, by example the 'date' field of 'fleet.vehicle.log.fuel').

addons/web/static/src/js/views/search_menus.js

@@ -416,8 +416,8 @@ return Widget.extend({
     },
     get_groupable_fields: function (fields) {
         var groupable_types = ['many2one', 'char', 'boolean', 'selection', 'date', 'datetime'];
-        var filter_group_field = _.filter(fields, function(field, name) {
-            if (field.store && _.contains(groupable_types, field.type)) {
+        var filter_group_field = _.filter(fields, function (field, name) {
+            if (field.sortable && _.contains(groupable_types, field.type)) {
                 field.name = name;
                 return field;
             }