Hide popup panel after successful autofill

If an autofill successfully fills one or more fields, close the popup
panel so the user can carry on interacting with the site.
Do not autofill hidden fields

Avoid filling fields in hidden modal dialogs on pages etc.
by only filling fields which are actually visible.

Some sites use a popup overlay for the login form itself so
this behavior may need to be revised.
Set Alt+Shift+P as the default shortcut to show the passcards panel in Chrome

This matches the shortcut used in Firefox.