Support reset password screen

Hi Steve,

I hope you don't mind, but I've spent some time this morning to extend your great Force Strong Passwords plugin to also support the reset password facility on the login screen. I have a client where I need to force all the admin users to reset their passwords, and I want to ensure the new passwords are strong.

I've split the main function into two to do this, and also changed the way the conditionals work so that it runs through a number of `if` checks and returns if they fail the conditions. I felt this made things easier to read, but let me know if you're happier with your original form.

Any issues, I'm happy to look at changing things around.

Cheers,

Simon