groups in profile layout change

when groups are added to a search profile, the checkbox list of groups is generated in html as a long list, with no breaks between each group, and no effective way to alter the layout via css.

the attached patch adds a break tag after each group to list the groups one to a line. that's more scalable (for 2-3 groups the existing layout may be fine, but any more and it becomes unusable). ideally each element should be wrapped in a span or div tag so the layout can be decided outside of code, but the quickform addgroup function doesn't give much control to do that (as far as I can see)