Wrap row classes in a filter on the group admin screen

See #5173

Props imath

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7378 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Use row classes in group templates

bp_group_class() provides valuable CSS classes for use in groups loops
(such as 'odd' and 'even'), and also provides a way for plugins to
style rows in various ways using the included filters.

Fixes #5173

Props imath

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7379 cdf35c40-ae34-48e0-9cc9-0c9da1808c22