Add config for new Memcached features

Adds config for persistent connections, SASL authentication, and custom options

config/cache.php

@@ -49,6 +49,14 @@ return [
 
         'memcached' => [
             'driver' => 'memcached',
+            'persistent_id' => env('MEMCACHED_PERSISTENT_ID'),
+            'sasl'       => [
+                env('MEMCACHED_USERNAME'),
+                env('MEMCACHED_PASSWORD'),
+            ],
+            'options'    => [
+                //Memcached::OPT_CONNECT_TIMEOUT  => 2000,
+            ],
             'servers' => [
                 [
                     'host' => env('MEMCACHED_HOST', '127.0.0.1'),