Tweak url formatting

See http://forums.musicbrainz.org/viewtopic.php?id=5394 for original
issue (with discogs) and proposed fix.

This tweak goes slightly beyond this, only providing a specific port if
it is not 80 or 443.
Merge pull request #386 from Sophist-UK/drunkendwarf_webservice_noport

Use https if port 443 is specified, and only provide a specific port if it is not 80 or 443.