I'm imagining elements in a queue that correspond to a particular class/struc format being added to a master list by an arbitrary account. Any easy way to create such a list via a contract? I'm also interested in clearing out the list every given time interval, and eliminating specific elements of the list on demand. I'm hoping for something analogous to how one would manipulate an array or std::vector, but maybe that's asking too much. My understanding is that eosio::multi_index is the only way to store persistent data on the eos blockchain. Please correct me if I'm wrong; I'd prefer to use array or std::vector if that's an option.