fix(form-group): update margins & support static forms

CI had some issues without margin-bottom for .form-group.

This keeps the default .form-group margins and adds support for .form-horizontal-static to enable detail page type styles with form-group's. Might be a breaking change for people depending on this but it's nothing disastrous.
I just checked out the default Bootstrap progress bars, and they don't have a bottom margin. Unless someone added a rule for it, we can probably scrap this.