[sldev] "parcel" media should include the ability to set local host, at least in a HUD instance

[Lawson English]

I can imagine many cases where a  media plugin served from localhost 
might be useful. It should be possible to pecify localhost as a valid 
url for media-on-a-prim (HUD at least) that is settable separately from, 
or as an alternative to, the parcel media URL.


IOW, if I install a custom HUD with a localhost url as the parcel media 
url, I should be able to interact with a private plugin running on my 
own comp.

Lawson