Welcome back BeatmapManager
# Conflicts: # osu.Game.Rulesets.Mania/UI/Column.cs
Gets ArchiveReader out of WorkingBeatmap and delegates extracting stuff from it to subclasses. Should enable us to make an OnlineWorkingBeatmap or so.
Note, that circle sizes still are wrong compared to stable osu. In order to fix this, the base radius of hitcircles needs to become 64, but it currently is 72.