Add the option to do predictions by match instead of map

[slmnio]

The new automatic predictions system from #141 is great and has worked pretty flawlessly. However, predicting each map instead of the match has some problems:

• Producers get busy and forget to do every single map
• Map predictions get low engagement because they're open for a short time, and viewers much prefer to bet for the entire match.

My proposal for changes is:

• Add logic to understand if a match has been won or not (match.first_to). We don't need to worry about looking behind for previously played matches, it should be fine just using the active broadcast.live_match
• Make match predictions default over map predictions
• Add a broadcast setting (broadcast.broadcast_settings) to override to map predictions

[slmnio]

@ZusorCode might be up your alley