Mu Multi S Server C Cache Cl Clear

A more focused cache clearing mechanism across multiple web heads running Magento.

The old MSCC cleared all cache in var/cache byt issuing a "rm -rf var/cache/" from the webroot. It was extended to also "rm -rf var/full_page_cache/" from webroot at a later time.

The module will rely on: --configuring the servers that are in rotation --executing a command on each server that will implement the proper Magento way to clear the given cache type(s).