Slider speed mod

[MightyHelper]

Describe the new feature:
Will scale the map playback speed so that the sliders always go at the same speed visually.
eg: Say a map starts with a slider speed of X, then it encounters a 2X section, the playback will slow down to 50%.
Proposal designs of the feature:
Probably won't work as intended on all maps but.
XP multiplier should depend on map.
Also, star rating should be recomputed.