Add password generator

[Gear61]

V1 features:

1. Password length (1 to 128)
2. Needs a capital letter
3. Needs a special character (!, @, #, $, %, ^, &, *)
4. Needs a number

We can just generate an alphabetical lower-case string and then go through each constraint and replace a character at random if it's ticked in.

[DonaldTsang]

And also add a password strength tool to it. zxcvbn is very effective.

Another idea: passphrase based on words in an arbitrary wordlist OR 5d6 / 3d20 (please check https://github.com/grempe/diceware/issues especially the ones that are closed)