Reselect visit attribute values on error

When you are saving a Visit that has at least one VisitAttributeType, the values of the attributes that the user entried should be repopulated into the fields when redisplaying the field with an error.

To reporduce:
Create 2 VisitAttributeTypes of boolean
Set the types to 1 min, 1 max
Try to create a new visit but don't select the value for one of them. Neither yes/no/true/false is checked when the form is shown again.

(didn't test whether string values are repopulated or not)