Visit form update

1) Handel unit type (lb&ft / kg&m).
2) Caculate BMI in controller.
3) H / W data store in DB are metric unit. Convert to imperial when
rendering in view.
4) Input restraint for meet the format of height and weight
Merge branch 'master' of github.com:bumetcs/cs673

Conflicts:
	app/Controller/VisitsController.php
	app/View/Visits/add.ctp