Should add a new function for contract update (with storage migration)

[riversyang]

It seems the function deploy_and_init of near.rpc.Client should only be used to deploy and initialize a contract. (I also think the init function name of Octopus contracts can be fixed as new.) But when we update a contract with storage migration, it's better to perform the code deployment and migration in one transaction. Or the contract may become unavailable if the migration function fails.

I think we should add a function in cli to perform store_wasm_of_self function and then update_self function of a contract. (We can use these two function names in all Octopus contracts.)