When saving passwords only save (sub)domain

[rugk]

In order to use #64 in a sane way, it makes sense to only save the protocol and full domain when adding a password via the add-on.

Otherwise you get entries like:

• https://example.com/login.php?confirm
• https://example.com/good-forum/some-forum-thread-32783
• https://example.com/confirmmail.php?id=jfhe789r3…
• …

This is useless. Actually, I'd say it is very unlikely that the subdirectory is a different website with a different (login) password. Thus, I'd enable such an option by default.

Do not save the subdirectories (full URL), but only the important part.