Resolve "The "radio - random" function also plays podcasts"
Closes #1140 (closed)
Add a content category filter to the automatically generated radios (random, less-listened, favorites) so that they only play music and don't include podcast content.
It may be nice in future to add a radio specifically for podcast discovery/content filters in the radio builder to allow users to specify content categories. This change makes the radios follow their original function.