Added Rdio content provider, Fixed spotify content provider result title, Fixed Http.GetAsync to handle WebExceptions.
Added ContentProvider Priority (to allow giving priority to one content provider over another), Added Repository property to allow content providers access to database.

These changes are part of the initial work to be able to finish MusicServiceContentProvider (Music links with content localized to their preferred music service).
Added completed PlexrContentProvider, Added task weight ordering to ResourceProcessor, Renamed ContentProviderResult Priority property to Weight.
Fixed PlexrContentProvider when returning null on rdio.com/artist urls that aren't supported.
Finished client-side for Plexr support.