Adds/Updates the item's data from the instance's storage system.
{"msg":"set_storage","instance_guid":"my_session_id_here","Item":"foo","Data":"bar","passkey":"insert password here","role_id":"superadmin"}

The server will add the item to the session storage:
{"MSG":"put_storage","Item":"foo","Data":"bar","Password":"insert password here"}

If the item exists (and if password was set and is correct):
{"MSG":"update_storage","Item":"foo","Data":"bar"}

If the item exists but the password is incorrect:
{"MSG":"update_storage_password_failed"}