Allow `bp_core_admin_tabs()` to be filtered.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7630 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Improve return/break logic in `bp_core_add_contextual_help_content()`.

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7631 cdf35c40-ae34-48e0-9cc9-0c9da1808c22