allow storage of url (the saved url has additional info about user)

I.
When zeroid could save an url (1) from the user,
other services like e.g. zerotalk could use this info from zeroid
to make the username clickable with this url

the url is in most of the cases a ZN address,
where the user details more info (blog, homepage, gpg key, hobbies, ...)

so e.g. ideas like this would be possible: https://github.com/HelloZeroNet/ZeroTalk/issues/13

II.
this feature would need:
adding url
editing url in future
deleting url (deleting is a sub case of editing)

(1) it must be not a complete url, but only everything that comes after http://127.0.0.1:43110/