Migrate mania to use the new difficulty calculator structure
Migrate catch to use the new difficulty calculator structure
Migrate osu to use the new difficulty calculator structure
Fix TestCaseMultiScreen intermittent failures
# Conflicts: # osu.Game.Rulesets.Catch/Difficulty/CatchLegacyDifficultyCalculator.cs
# Conflicts: # osu.Game.Rulesets.Mania/Difficulty/ManiaLegacyDifficultyCalculator.cs
Implement new difficulty calculator structure
# Conflicts: # osu.Game.Rulesets.Osu/Difficulty/OsuLegacyDifficultyCalculator.cs
Fix test dlls being loaded as actual rulesets (and failing)
Add "Grow" mod