Memcached Multi Plugin Overhaul

Had these changes staged for some time now, decided to let them out into the wild.

This new version allows for more control over what commands are put into the commands graphs, and subsequent slab graphs.

I've made the main root graphs now show on the subpage so they can be dug into more deeply with the dynamic zoom feature.

I've also updated the plugin to run against the latest version of memcached, v1.4.15.

I've added a new graph called unfetched, showing expired and evicted items that were never touched in any means.

Bugfixes, updated documentation, and other various changes have been included as well to make the plugin work correctly across many various versions of memcached v1.4.x