Add additional accounts

Provide the option to connect additional accounts individually, rather than in packages. Also provide the option to retain the data from these individual accounts so that the account history is considered even after the connection is deleted, but without the permanent cost of the extra connection.This serves those who have accounts with old transactions that are relevant for evaluating spending profiles, but which are currently unused, or even those who have accounts that are now obsolete, but could have been the main account before.