Add the new MusicRate selector to Edit/Practice mode

[kubik369]

Hi,

I have added the new MusicRate selector that is default in Play mode to the Edit/Practice menu. I have been able to limit it to applying this only in the ScreenEditOptions, so I am fairly certain it should not break anything else.

Thanks for taking a look :)

[kubik369]

I have just noticed that the original PR did not work on the second playback of the song. I have written it in the comment above the code, so I will just paste it here:

-- The rate change needs to be set in ModsLevel_Song for it to work in Edit/Practice modes.
-- It needs to be set in ModsLevel_Stage too, otherwise the rate gets reset when playing
-- the song a second time. If it is set only in ModsLevel_Stage, it gets applied only
-- on the second playback of the song and the first one gets weirdly modified going in the
-- opposite direction, e.g. set a song to 0.50x and you get the arrows going double the speed.
local isInEditOptions = SCREENMAN:GetTopScreen() and SCREENMAN:GetTopScreen():GetName() == "ScreenEditOptions"
if isInEditOptions then
  GAMESTATE:GetSongOptionsObject("ModsLevel_Song"):MusicRate( self.Values[choice] )
  GAMESTATE:GetSongOptionsObject("ModsLevel_Song"):PitchRate( self.Values[choice] )
  GAMESTATE:GetSongOptionsObject("ModsLevel_Stage"):MusicRate( self.Values[choice] )
  GAMESTATE:GetSongOptionsObject("ModsLevel_Stage"):PitchRate( self.Values[choice] )
end

I have pushed the commit which should remedy this.