support password

[lehnberg]

• Allow users to optionally set a password.
• This is then required each time wallet is launched.
• Option to also set a "lock time" after a period of inactivity (configurable in minutes) that requires the wallet to be unlocked before it can be used again. During lock time, the wallet still listens (if listeners are active) and processes slates as usual - it's just the interface that's locked.
• Ability to remove password. Requires current password.
• Ability to change password. Requires current password.

[ravidio]

suggest to split this to 2 issues - the first is done with latest PR and can be closed. it covers:

1. setting a password when initiating a wallet.
2. is password is set wallet has to be unlocked using unlock command before accessing any of the wallet operations.
3. unlocked wallet can be locked again using lock

[lehnberg]

@ravidio I've updated this ticket instead to include checkboxes/progress bar.