These have been in release builds since January, but implemented in a hacky way. This brings them with a sane implementation.
This is not a great idea.
In line with stable editor restrictions
Resolves ppy/osu#1988.
Apaprently some ranked maps contain unordered hitobjects. We probably never want to allow for this.
This is what stable did.
Also removes unnecessary background texture (the actual storyboard background spec wasn't implemented correctly anyway).
Also moves delete and action logic to a shared implementation
Also add finaliser logic for safety. Also better threading. Also more cleanup.
Not yet working