Expose Menu_Stats _selectedAchievmentId, and other secret menu data

[piber20]

Expose _selectedAchievmentId so mods can see what achievement ID is currently visible in the secrets menu.

Consider exposing other data too, such as the min and max displayed achievements (for up/down scrolling when viewing mod unlocks) and the achievements associated with the mini sprites (they seem to track something since they can visually appear locked or unlocked)

[jsgnextortex]

Just as clarification, the achievements associated with the mini sprites are the achievements adjacent to the currently selected one....and, yes, they do change depending on if said achievements are unlocked or not.