Not really changing anything, just tightening things down to curb possible funny business.
LocalisableString
Also, mark as nullable for some properties.
IApplicableToSample
Done for consistency with `IApplicableToTrack`.
IApplicableToTrack
ModUsage.Solo
ModUsage.User
IsPlayable
Mod
approximatedRates
ratesForRewinding
applyPitchAdjustment
adjustPitchChanged
IUpdatableByPlayfield
ApplyToBeatmap
Enumerable.Repeat
average_count