+ Stopped using testing methods in non-testing classes
+ Resolve Player and add OnSeek event
+ Take bindings away from BarHitErrorMeter
+ Add support for ColourHitErrorMeter
It's not valid in the base `HitErrorMeter`, as the colour meter only
displays colour for a given judgement, so it is still valid to add new
items to it even if the hit window is 0, as misses are still possible.