Added Geohash Cell filter

Filter/GeohashCellFilter.php

+<?php
+
+/*
+ * This file is part of the ONGR package.
+ *
+ * (c) NFQ Technologies UAB <info@nfq.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace ONGR\ElasticsearchBundle\DSL\Filter;
+
+use ONGR\ElasticsearchBundle\DSL\BuilderInterface;
+use ONGR\ElasticsearchBundle\DSL\ParametersTrait;
+
+/**
+ * Represents Elasticsearch "Geohash Cell" filter.
+ */
+class GeohashCellFilter implements BuilderInterface
+{
+    use ParametersTrait;
+
+    /**
+     * @var string
+     */
+    private $field;
+
+    /**
+     * @var mixed
+     */
+    private $location;
+
+    /**
+     * @param string $field
+     * @param mixed  $location
+     * @param array  $parameters
+     */
+    public function __construct($field, $location, array $parameters = [])
+    {
+        $this->field = $field;
+        $this->location = $location;
+
+        $this->setParameters($parameters);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getType()
+    {
+        return 'geohash_cell';
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function toArray()
+    {
+        $query[$this->field] = $this->location;
+        $output = $this->processArray($query);
+
+        return $output;
+    }
+}