Don't strip comments when calling ParseLine
With .NET core 2.0+ this is as efficient as the ugly code we've been using.
Closes #2731.
Closes #2966. --- Was causing some beatmaps to not play all of their hitsounds
Resolves #2970.
- Add a download failed event to BeatmapManager - Make DownloadButton aware of all 3 possible download states - Change button appearance based on each state
/shrug