added "--cli" option to apc:clear command

I have a variety of servers in production, some of which have a web presence, some of which do not.  I need to clear the APC cache on all of them, but the command currently only takes care of clearing the cache via the web.  I can't use the command to clear caches on the machines that are only doing cli work.

This just adds a `--cli` option to the current command, which will clear the cache via the CLI, instead of the web.