(Bug 5084) Rename Planet Caravan props to match standards

$color_journal_subtitle -> $color_page_subtitle
$color_alternate_entry_border -> $color_entry_border_alternate
$color_alternate2_entry_border -> $color_entry_border_alternate_second
$color_alternate3_entry_border -> $color_entry_border_alternate_third

All previous themes updated to use renamed properties.