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.
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
Collapse visual settings by default in player
Also removes unnecessary background texture (the actual storyboard background spec wasn't implemented correctly anyway).