Update item location field to match URLs list on save

When saving an item, set the location property in the overview
to match the first URL in the item's URLs list.

The URL is duplicated in the overview data and the encrypted content
for use when searching items.
Improve URL matching where item URL is missing a scheme

Since URLs are effectively free-text entry fields they may
not have a scheme. Normalize the URLs before parsing them
in item_search and if no scheme is provided, assume HTTPS