Update hook fixes home menu items.  #3491

Had to change my approach a little.  The menu item alone wasn't enough to figure out if an external link needed a change or not.  I added custom domains and purl to the query, then built up a list of urls to change:  home, /home, $domain/home, and $domain/$purl/home (where domain is either the custom vsite domain or the purl base domain).  Those get removed from the menu path and I don't touch any other urls.
Default domain is base_url #3491
Merge pull request #3506 from openscholar/3491-home_update

Update hook fixes home menu items.  #3491