Add or filter doc.

docs/Filter/Or.md

+# Or Filter
+
+> More info about or filter is in the [official elasticsearch docs][1]
+
+A filter that matches documents using the OR boolean operator on other filters.
+
+## Simple example
+
+```JSON
+{
+    "filtered" : {
+        "query" : {
+            "term" : { "name.first" : "shay" }
+        },
+        "filter" : {
+            "or" : [
+                {
+                    "term" : { "name.second" : "banon" }
+                },
+                {
+                    "term" : { "name.nick" : "kimchy" }
+                }
+            ]
+        }
+    }
+}
+```
+
+And now the query via DSL:
+
+```php
+$termFilter1 = new TermFilter('name.second', 'banon');
+$termFilter2 = new TermFilter('name.nick', 'kimchy');
+
+$orFilter = new OrFilter();
+$orFilter->add($termFilter1);
+$orFilter->add($termFilter2);
+
+$termQuery = new TermQuery('name.first', 'shay');
+$filteredQuery = new FilteredQuery($termQuery, $orFilter);
+
+$search = new Search();
+$search->addQuery($filteredQuery);
+$queryArray = $search->toArray();
+```
+
+[1]: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-or-filter.html