Add back memcached

src/Config/ConfigInfo.php

@@ -146,17 +146,46 @@ class ConfigInfo {
     /**
      * Support memcache for session caching
      *
-     * Store sessions in memcache - this seems like the fastest, best, and simplest approach
-     * when running on AWS.
+     * Memcache is php-only and so is likely to require less overall dependencies.
      *
-     * http://php.net/manual/en/memcached.sessions.php
+     * http://php.net/manual/en/memcache.sessions.php
+     *
+     * Installed on Ubuntu using
+     *
+     * apt-get install -y php${TSUGI_PHP_VERSION}-memcache
      *
-     * Note - prefer "memcache" over "memcached"
+     * You should only select one of memcache and memcached
      *
      * $CFG->memcache = 'tcp://memcache-tsugi.4984vw.cfg.use2.cache.amazonaws.com:11211';
+     *
+     * In addition to setting this variable, your config.php must include the code
+     * to configure the PHP session save handler as shown in config-dist.php
+     *
      */
     public $memcache;
 
+    /**
+     * Support memcached for session caching
+     *
+     * Memcached is a combination of PHP and C and so may require extra dependencies.
+     *
+     * http://php.net/manual/en/memcached.sessions.php
+     *
+     * Installed on Ubuntu using
+     *
+     * apt-get install -y php${TSUGI_PHP_VERSION}-memcached
+     *
+     * You should only select one of memcache and memcached
+     *
+     * $CFG->memcached = 'memcache-tsugi.4984vw.cfg.use2.cache.amazonaws.com:11211';
+     *
+     * Note no "tcp://" for the memcached version of the url
+     *
+     * In addition to setting this variable, your config.php must include the code
+     * to configure the PHP session save handler as shown in config-dist.php
+     */
+    public $memcached;
+
     /**
      * Adding in support for using Redis for session caching.
      *