Add option to append error text to the in-valid element's parent control-group.

[mikewaters]

Currently the code appends the validation error message (a span.help-inline element) to the element that has failed validation.
This patch creates the option ('append_to_control_group') to append that error message element to it's parent control-group instead.
Reason: I have a form where inline elements are arranged in a columnar layout, like:

first-name       last-name
home-phone       cell-phone
email-address
submit-button

The validation error message for 'first-name' would break the layout, inserting the span.help-inline between first-name and last-name.
Assuming that first-name and last-name compose a control group, the error message would appear on the next line, keeping the layout intact.

Thanks,
Mike Waters