Add torrent by info hash

[fx]

Id like to be able to add torrents just by info hash instead of full url or a full magnet link:

To download from just a hash i simply prepended a magnet link to the front of the url:

if(url.match(/^[0-9a-f]{40}$/i)) {
    url = 'magnet:?xt=urn:btih:'+url;
}

I have put this in AddTorrentByUrl? function in transmission.remote.js but im sure it could have a more fitting home

[fx]

Been testing this for about 2 months, and works pretty sweet. For popular torrents (or if you have lots of peers connected) we just share hashes around

[bulljit]

@fx

i personally don't use magnet links... but very cool! well done.

[livings124]

r12501

Thanks!