Make removing the fieldset around address fields optional

Currently the Customer module removes the fieldset around address fields that are displayed in the context of the checkout form or customer profile reference manager widgets (i.e. order add / edit form). This is a bit of that "magic configuration" that we worked hard to stamp out of the Add to Cart form / product attributes systems. In this case, I think it would be preferable for the Customer module to add a checkbox option to address field settings on Customer Profile entity types to remove this fieldset that defaults to TRUE.

I came across this issue b/c I was updating the code to fix #1234258: Update commerce_customer_field_widget_form() to remove the fieldset from any address field when I realized this wouldn't properly accommodate profile types with multiple address fields (be they few and far between). Right now I'm just leaving the fieldset in the case of multiple address fields, but it would be nice to give the administrator the option to remove it around just one.