Add "Add New" link to Dashboard > Groups header.

Fixes #4987

Props imath

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7006 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
POT, generated from r7006

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7007 cdf35c40-ae34-48e0-9cc9-0c9da1808c22