Add height as a DecimalField to BmiForm
Add height as a DecimalField to BmiForm

If the form got a floating point value in the height field, then
the validation failed. Because of this the bmi calculation didn't
return anything. Fixes #146

rolandgeider/wger,wger-project/wger,DeveloperMal/wger,kjagoo/wger_stark,DeveloperMal/wger,kjagoo/wger_stark,kjagoo/wger_stark,petervanderdoes/wger,rolandgeider/wger,kjagoo/wger_stark,wger-project/wger,DeveloperMal/wger,DeveloperMal/wger,petervanderdoes/wger,wger-project/wger,petervanderdoes/wger,rolandgeider/wger,petervanderdoes/wger,wger-project/wger,rolandgeider/wger