Add information to replay beatmap comparison

[blimmo]

The current return of replay.hits is simply a dict mapping score to HitObjects. Since the method for calculating this also includes a lot of extra information that is lost I thought returning all this information in an object might be better.

What's here is still a bit rough but I thought I'd push this here now since we should probably get this in master as soon as possible if it's going in at all since it's a backwards incompatible api change.