Remove osu! playfield scale from the editor
Fix editor layers not respecting playfield aspect ratios + scales
Expose SliderBody's snaking and border colour
Fix stacking not working with sliders
Fix some common CI unit test failure causes
Fixes #2093.
As seen here: https://ci.appveyor.com/project/peppy/osu/build/master-7260#L1164 Potentially was continuing operation too early.
And make it more general.
Move manual OsuPlayfield aspect adjustment into the RulesetContainer method
Combine border radiuses of selection and capture boxes
Improve testability of API
Rewrite editor hitobject selections
Give storyboards a BeatmapInfo to reduce weird method calls
Fix replay import
Abstract away model-filemodel and add mutable stores