Migrate all usages of StreamReader in the context of decoding beatmaps, storyboards or skins to the new LineBufferedReader.
# Conflicts: # osu.Game.Rulesets.Catch.Tests/CatchBeatmapConversionTest.cs
TRuleset was a mistake. This resulted in cases that checked whether the beatmap was for the current ruleset (TaikoBeatmapConverter and ManiaBeatmapConverter) failing due to TestXRuleset != XRuleset...