Improve 'Radio Mode' Algorithm

[MeoMix]

SongBuzz currently supports 'Radio Mode' as an option under settings.

We should consider if this is an option that should be toggled on/off through the settings menu. Perhaps it should be displayed in the GUI at all times, though, like the shuffle button. I do not believe people shuffle their music as much as they would turn 'Radio Mode' on and off.

Currently, this is how 'Radio Mode' works:

• A playlist contains a collection of videos.
• The YouTube API is able to provide the 'Related Videos' for a given video ID.
• The playlist maintains a collection of 'Related Videos' for all videos in the playlist.
• Pick at random from related videos collection.
• Add random song to playlist and begin playing it. Note that adding the random song to the playlist causes the playlist's collection of Related Videos to be modified.

This allows for a very simplistic, evolving related videos structure. However, there are some issues which need to be addressed.

• Don't pick at random. Instead, inspect the meta data for the related videos, weight them based on something (tag? similiar artists in playlist?), and play based on best fit.
• Shouldn't allow for randoming into a song that is already in the user's playlist.
• Sometimes songs which are banned come up. Should discard those results.
• I think I am storing too many related videos. Large playlists may contain thousands of related videos, but really we only want 1 related video at a time.

[MeoMix]

Another note for weighting of music -- suggested videos of suggested videos tend to be poorer than the first query's collection. Each iteration of suggested videos should be more difficult to random into, but this chance should not be 0%.