display of group(s) options in profile for contribution form

In working through CRM-8289, I noticed another difference between how the "group(s)" checkboxes appear in a profile that's part of a contribution form versus standalone in create mode. templates/CRM/UF/Form/Block.tpl created a table with a single cell and plopped all the groups there, divided only by line breaks. It's difficult to theme that.

On the other hand, a profile on its own uses templates/CRM/Profile/Form/Dynamic.tpl, which includes templates/CRM/Contact/Form/Edit/TagsAndGroups.tpl and its much improved display of groups in separate rows with IDs.

I've attached a patch that implements this in the context of a profile block within another form. I had to set $title as null; otherwise it would try to put the field within an accordion labeled with the title of the contribution page.