Update Memcached To Use New Directory Structure

Currently the memcached builder is in `services/memcached/builder.js`

We're now using a directory structure that looks like `builders/memcached.js`...most other plugins do this.

We should update memcached to follow that pattern, and update all the recipes that use memcached to require it by that new `builders/memcached.js` path (looks like currently just Acquia and Symfony).