Added count_multi() to record dao.
Removed specialized/redundant meta cache functions, and used the more generic functions in their place.
Renamed entity_record_dao::limits() to entity_record_dao::limit_multi() to make it more consistent with the naming convention.
Added key_prefix override for redis. Each named redis server can have its own key_prefix that overrides the default.
Disabled the $list_items_to_remove code from meta cache deletion functions, since this can cause race conditions, kinda sucks this needs to be removed, but it's possible redis will support a command in the future that allows for the deletion of empty sets...  *crosses fingers*