[RCD] session storage driver plugin support

Hey all, I recently submitted two PRs to refactor session storage. The first made it possible to hook into sessions, which get initialised very early in the code execution path. The second refactored session storage drivers into separate classes and added redis as a session storage driver.

Both PRs were accepted, so for people wanting to experiment you can use redis as a session store in the master branch. I also created a sample plugin that adds php-memcached (not to be confused with php-memcache, they are two different PHP memcache options) as a session store.

You can find the example plugin here: https://github.com/corbosman/session_memcached https://github.com/corbosman/session_memcached

Cor