TOTP icon improvements

[varjolintu]

Ignores TOTP field icons when input field type is password or input field name/id begins with zip/postal and ends with code.

Fixes #768.

[droidmonkey]

I have seen some TOTP fields that are password fields, for some dumb reason. I cannot recall an example right now, but be prepared if this breaks someone's workflow. I think the password field might be too broad of a discriminator.

[varjolintu]

@droidmonkey I'm aware of that. Sadly it's expected that something always breaks because the sites just doesn't use the standard option(s) for these.