Add filtration usage doc and missing config options

Author: MisatoTremor

doc/pager/config.md

@@ -19,6 +19,8 @@ The list of existing options are:
 | sortFieldWhitelist         | array          | []            | SortableSubscriber                              |
 | sortFieldParameterName     | string         | sort          | SortableSubscriber                              |
 | sortDirectionParameterName | string         | sort          | SortableSubscriber                              |
+| defaultFilterFields        | string\|array* |               | FiltrationSubscriber                            |
+| filterFieldWhitelist       | array          |               | FiltrationSubscriber                            |
 | filterFieldParameterName   | string         | filterParam   | FiltrationSubscriber                            |
 | filterValueParameterName   | string         | filterValue   | FiltrationSubscriber                            |
 
@@ -45,3 +47,8 @@ you have to set `wrap-queries` to `true`. Otherwise you will get an exception wi
 Used as default field name for the sorting. It can take an array for sorting by multiple fields.
 
 \* **Attention**: Arrays are only supported for *Doctrine's ORM*.
+
+
+### `defaultFilterFields`
+
+Used as default field names for the filtration. It can take an array for filtering by multiple fields.

doc/pager/usage.md

@@ -95,3 +95,19 @@ $pagination = $paginator->paginate($query, 1/*page number*/, 20/*limit per page*
 
 The Paginator will add an `ORDER BY` automatically for each attribute for the
 `defaultSortFieldName` option.
+
+## Filtering database query results by multiple columns (only Doctrine ORM and Propel)
+
+You can also filter the result of a database query by multiple columns.
+For example users should be filtered by lastname or by firstname:
+
+```php
+$query = $entityManager->createQuery('SELECT u FROM User');
+
+$pagination = $paginator->paginate($query, 1/*page number*/, 20/*limit per page*/, array(
+    'defaultFilterFields' => array('u.lastname', 'u.firstname'),
+));
+```
+
+If the `filterValue` parameter is set, the Paginator will add an `WHERE` condition automatically 
+for each attribute for the `defaultFilterFields` option. The conditions are `OR`-linked.