Remove default wrapper classes

Hi,

i want to remove all classes from the group wrapper, except the one i added on my own. im using a bootstrap layout and currently it looks like this (i removed the fields):

<div class="field-group-format group_startseite_row1 field-group-div group-startseite-row1 row speed-fast effect-none">
    <div class="field-group-format group_startseite_text field-group-div group-startseite-text span9 speed-fast effect-none">
    </div>
    <div class="field-group-format group_startseite_kontakt field-group-div group-startseite-kontakt span3 speed-fast effect-none">
    </div>
</div>

But i would like to have this:

<div class="row">
    <div class="span9">
    </div>
    <div class="span3">
    </div>
</div>

I already tried #2 of this issue: Allow removing field group div classes but it doesnt worked.

In addition it would be very nice to have an option in admin ui or a theme file where i can delete / add default classes. But for now im just looking for a quick fix (in template.php?).

Greetings :)