Rename and Add Extra Repo

I've renamed the xbmcnightlybuilds to XBMCNightlyBuilds (Nightly Builds).

I've also added and additional source - XBMCNightlyBuilds (Official Stable Builds Mirror) - this is a mirror of the official sources site, however is using my CDN network to distribute the load / redirect users to their nearest mirror. You can find out more details here - http://xbmcnightlybuilds.com/mirrorbrain-new-download-mirror-system/

I thought the ArchiveLinkExtractor would have worked with it, but I'm not sure it is looking at the correct url - could you confirm this before merging?