Add remember_me login flow

[pfferrari]

Add the Remember me checkbox below login form fields.
If you click the Remember me checkbox before submitting the form obtained customer data will be stored in localStorage.
This way the customer token will be available for future login attempts and, if valid, will be used to login back the customer without showing the login form (loading status).
Stored customer token will take advantage of refreshToken in order to be respawned if refreshToken is still valid otherwise the login form will show and corresponding customerToken localStorage will be removed.

[pfferrari]

@marcomontalbano @malessani does this idea for remember me flow look good for you?