Option to save the password

add a setting to store the password with the hint to the user that this makes things less secure

Motivation this will help developers when developing the app because it reduces the time they have to enter the password could also help adoption as a users might get frustrated having to enter a password often. There are some use cases where this additional attack-vector does not really matter and could be traded for convenience. Ideally this setting is exposed to the contacts so they know.

this is a follow up from a discussion in #587 (closed)