Heart calories

This adds a system for calculating the calories burned by the player from an entered heart rate and other data.
It's a bit clumsy, there's a flag in the profile that disables the step count based calorie counting if true.  This is meant so that a theme can check that flag and bring up a screen for entering the heart rate between ScreenGameplay and ScreenEvaluation.  _fallback and default themes do not have support for this because I do not want to spring an unexpected extra screen on themers that are not specifically looking to support it.  Docs/Themerdocs/calories.txt explains what a theme should do to support this.