convert change in probability to probability

[mattansb]

Change to Probs

• OR to prob
• logOR to prob
• RR to prob
• ARR to prob
• NNT to prob

@strengejacke @bwiernik

• Do we also want the inverse of these? (e.g., prob to OR)
• Do we also want conversion to odds? (e.g., NNT to odds)

originally posted on #568