Add autocomplete="off" to login widget and form password fields

[netweb]

Browsers (IE, Chrome, Firefox) no longer respect autocomplete="off" on <input type="password" /> fields.

Via ​#BuddyPress6269 and ​#WP24364

This is the best summary from @hnla rounds it up well: ​https://buddypress.trac.wordpress.org/ticket/6269#comment:3

​https://bugzilla.mozilla.org/show_bug.cgi?id=956906

The summary from a very long thread from a Mozi discussion on the subject:

Summary of the change, so people don't have to wade through a long discussion:

• This change makes it so that autocomplete=off does not stop the Password Manager >from working. Normal form autofill can be disabled as usual.
• The password manager *always* prompts if it wants to save a password. Passwords are >not saved without permission from the user.
• We are the third browser to implement this change, after IE and Chrome.
• This can be undone locally by flipping the signon.storeWhenAutocompleteOff pref >(from about:config) off.
• The rationale behind this change was the widespread abuse of the autocomplete >attribute to prevent password saving where no prevention is required. This change gives >users full control over password saving, without compromising on security (again, the user >is always prompted).

Seems overall that autocomplete=off should be implemented, the main concern in doing so being that preventing browsers auto saving to password managers would be a very bad thing possibly resulting in people using weak passwords where they might have been using very strong ones in the knowledge that a browser action by user would have the password inserted to field.

It seems that Mozi here acknowledge that they are the last to implement a fix for autocomplete disabling their password saving thus all major browsers are safe in this respect and my 20 char passwords will be automagically inserted regardless of autocomplete set.

[pareshradadiya]

Added 'autocomplete="off"' to password field

[netweb]

In 5793:

Add autocomplete="off" to password field on login widget, user login form, and converter form.

Props pareshradadiya. Fixes #2772